Fighter is probably the most gear/PL dependent class in the game, though it is not as bad as it used to be since the addition of Second Wind. You may find it easier to get through this class when you have better gear even if it requires you earn more XP.
That said, it depends on what difficulty you plan to play on. In heroics a Kensei wearing heavy armor with Stalwart Defense can kinda faceroll most of the game especially on elite since there is no self healing penalty. As you get into reaper and add more skulls PRR becomes less efficient compared to Dodge, your healing becomes ineffective, and your TTK too high to just heal between fights. Depending on your use of tactics (real tactics not just the CC abilities) and micro you can definitely overcome these difficulties to some degree (gear/PLs are more important than skill in this game and skill will never outperform them).
For your second life I think assuming you will be playing mostly on elite with some r1 in groups is probably most reasonable. It also seems like you are planning to TR at 20. In that case I suggest 18/2 Ftr/Rog. This will give you full UMD ranks, the ability to do traps if you want for more XP or when you have to (I think a high PRR/MRR build can probably face tank almost every trap in heroic on elite difficulty), access to Wand and Scroll Mastery, and Evasion if you need it. The only sacrifice you make is not having the Kensei 18 core at level 18 or the 20 core at 20.
I would build Str, THF, main Kensei with 13 points in StD for full PRR/MRR Stalwart Defense stance and Strong Defense (+6 Str in that stance). For a heroics only build I would recommend taking Cleave and Great Cleave as they are extremely strong when you can get them and they are never strictly bad (they don't benefit from Strikethrough but they can hit more targets, have +[W], benefit (and suffer) from attack speed modifiers as well as Double Strike, can be used to start attacking out of some actions with high end lag faster than LMB). I really like Stunning Blow because I think it is both useful and fun but you may opt to skip it if running elite only, and with low PLs and limited OP gear it may be unreliable, but I'd say adding more CC on Fighter is very good. Use heavy armor to benefit from Stalwart Defense and the Fighter exclusive heavy armor feats for more PRR/MRR, swap to light armor as needed for Evasion. I recommend ignoring Dex and dumping filler points into Int for more skill points and higher Search/DD, you may want to consider Insightful Reflexes to convert your Reflex save from Dex to Int to benefit from this (Reflex saves are still really beneficial in heavy armor: if you run through a blade trap and save without Evasion you will take half damage, if you also have 100 PRR (50% DR and very achievable) you will halve the remaining damage. Don't bother taking the lower tier Fighter exclusive feats, only the tier 3 and 4 versions are worth the investment, IMO. Take Liquid Courage in Kensei (if you have decent HAmp chugging Cure Serious pots and using Second Wind is extremely viable healing for elite; before Second Wind, chugging pots with Liquid Courage meant there was essentially zero risk of dying until certain quests in late heroics). If you can slot mana gear you might consider picking up KtA (if you have Harper) around 14 but it isn't particularly necessary or impactful in heroics. Halfling is an often recommended race for the healing Dragonmarks, WF is not bad for the immunities, Human is very solid for some cheap HAmp, a cheap boost for perma boosting, and the free feat.
Some general tips:
-Have/get UMD gear. Gear with +Cha and +UMD, or at least +UMD is really valuable to have even as a swap. Even if you only swap to it to use Heal scrolls OOC it is still very helpful. Also Restoration scrolls for neg level or high amounts of stat drain.
-Death Ward clickies. You can farm BtA goggles with one 7 minute charge from the end reward of TRG (not 100% chance, I think) and a hat from SM with three 10 minute charges. I'd have more rather than less, even if you think you have enough duration to cover getting to rest points, consider that more casts act as dispel protection. Primarily this effect is to prevent level drain, which is one of the more dangerous things that can happen to you, but if you don't have a DB item or augment for every level then DW becomes that much more important. If you have any spell absorption items you can equip them around Beholders so that your DW and other magical buffs do not get dispelled.
-If using Liquid Courage you can drink a potion before using a larger heal to get more out of it.
-See a caster, kill a caster. Stunning Blow and Trip are your friend.
-Generally Str will be your best overall stat since it gives you accuracy, damage, and tactics DCs. After main stat DStrike is definitely BiS without question as it represents a solid gain in overall DPS but can dramatically reduce HTK in fights if you get lucky making it very high value. I tend value Accuracy very highly as melee as a playstyle involves vomiting endless attacks at enemies hoping for crits until they're dead. With less gear you will definitely want to invest in Accuracy gear when you can as depending on content/difficulty you will not be hitting on a 2. On-hit effects (stun, prone, buffs, debuffs) are not applied on Grazes. If using tactical abilities you will want to invest in items that increase their DC.
-Without considering any exceptional weapons, I'd strongly recommend using Falchions at least starting at level 8 (or the earliest level you can take IC: Slashing). The base damage advantage of Great Axes is extremely negligible in heroics, they crit 43% as often as Falchions making them less reliable, their crits will be more prone to overkill wasting more damage, and Deadly Strike, a Kensei special attack causing a guaranteed critical threat, which synergizes better with GAxes than Falchions, has a 20 second CD and isn't really necessary (it's not bad for 1 AP though). Falchions will be more reliable as they will output more overall DPS while also giving your more consistent crits which are very impactful in heroics even with a x2 base mod. Greatswords I would only ever use as skelly/ooze/elemental/etc. beaters for the slight base damage increase if you don't have/use Fortification Bypass gear/attacks (you should though).
-Use Haste Boost. Haste Boost is a powerful DPS CD at end game and you get it at level 1. Especially in reaper, Fighter essentially tries to end fights as quickly and efficiently as possible in order to heal afterwards. On elite you can heal mid combat with Second Wind pretty comfortably but you may find yourself not having enough SW charges if you don't keep pace with Haste Boost uses.
-You can't Sunder incorporeal targets but you can Shattering Strike them for -15% Fortification. In quests with no Fortified targets, SS is still +1[W] every 10 seconds.
-Use Opportunity Attack before AoE, the MP buff will then benefit more hits giving you more overall damage and benefit from more hits allowing you to maintain better uptime. In single target if you are not getting charges back, save OA to use right before your other damaging special attacks to maximize their value.
-The magnitude of the Second Wind heal starts being calculated as half of your max HP but that number is then multiplied by HAmp meaning on elite your Second Wind can potentially full heal.
-Use Nightshield scrolls for MM immunity, they don't suffer ASF penalty.
-PfE scrolls will prevent you from being knocked down by Command spells. A long time ago there was a bug with PfE not functioning properly, if that bug still exists you may need to use Magic Circle of PfE which did work correctly.
Fireshield will prevent you from being webbed by natural webs and is a % DR against fire or cold damage.
-Before PRR Displacement was the auto-win vs physical damage in heroics. Carry some scrolls of this for hard fights, Blur scrolls or gear (also Ethereal/Ghostly gear) are very solid. There is an ML 3 trinket with permanent 20% Blur in Cerulean Hills which is easily farmable.
-The Bloodstone is probably pretty easy to farm nowadays (Antique Token turn in) has basically every DPS stat.
-There is no shame in using a Cleric/FvS hireling.
If you want a ranged Fighter build, go 8/6/6 Ftr/x/y. X/y can be Ranger/Rogue/Arti/Monk, choose ranged weapon accordingly. I would not go (melee) pajama build as you will not see a meaningful gain but will be much squishier and it is unlikely you will fill your Dodge Cap in heroic levels.
