A bit late to this party, but there are some really good ideas in this thread, and I'm hoping the devs at least read this at some point.
The issue of finishing moves is a strong one, and in an era where casters run around 1-shotting oranges, requiring a set of 4 button presses just to set up a finishing move is redundant. It's just never going to happen outside of solo, or VERY strategic gameplay. I really like the previous idea thrown out that we simply get access to a set of finishers (perhaps with varying ki costs) that we can hotslot. Sure, it'll take up more space on the bars, but it might mean they actually get used.
I also really like the idea of elemental strikes as imbues. They could be granted at level 1, similar to EK, and then grant +1 imbue when they would normally improve (@ 6, 12, 18). Additional imbue dice could be offered as enhancements, or as part of certain cores. This alone would improve Monk dps, especially the fast hitters like fist monk and ninja, dramatically. Henshin could use a few tweaks, but is in a decent spot already - at least for heroics.
Speaking of Ninja - the recent changes were nice, and allows them to focus on Assassination which I think is a good part of their identity anyways. However, the enhancement tree could still use some work. Poisoned darts is pure rubbish, and Diversion is questionable as well. And with the tree itself, it's always seemed odd that we start investing in Despair finishers when 2 of the 4 call for ninja poison - something you don't obtain for several levels. ToD is still very costly, and doesn't scale well at all - it really needs to double strike, crit, or *something*. Shadow Veil's 1 min duration is far too short, and could easily be fixed by X seconds per level, allowing it to scale with level. The tree offers some sneak attack, but not a massive amount to really make a difference at endgame; there's no melee power offered; an ability to AoE blind, but no means to do AoE damage (outside of WWA, which costs 3 feats); poison damage, but no immunity stripping; crit threat +1 isn't until T5, even though it's incredibly important to ninja poison; and crit mult isn't until level 18 (previously 20). It's just... weak.
I've played DDO off and on since Beta. I remember well the time of Ninja's origins, and it initially was *awesome*. But now it just hasn't aged well at all, and needs a fresh polish.
The latest balance adjustments were definitely appreciated, but more work is needed.