is there a guide to playing a tank? I feel certain there is more to it than just standing, shift-blocking and using intimidate.
There's more; in general grab agro and face things away from squishies. This isn't for rogues; they don't need the back. DDO "flanking" just means "someone else has agro".
If a squishy steps between you and a mob, the mob will hit them, not you. If someone flips a raid boss away from tank, it can take out all your DPS at once.
Hate helps a lot. My weird tank has ~250 MP and does huge dps compared to beefy push tanks, though still pathetic compared to a real DPS. For the most part, he locks agro very solidly. However, some bosses regularly zero all agro; eg. Suulomades. Having a way to get agro back quickly is important (knight's challenge).
It can help a LOT to have a leap or multiple leaps (spring, EA:C3, etc) to jump to the problem and re-intimidate. Many bosses will put chains on the tank making moving without a leap nearly impossible.
Dragon tanking is a toe-to-toe dance, which keeps them swiping rather than breathing. Toe-dance or circling is how tanks easily solo tank Kor-Kaza during the raid-split phases.
T-Rex roars can be negated by standing directly underneath.
Blocking is critical for some things, such as LOB's stun + wallop, which is usually an insta-kill if you don't block. Block prevents stone-grab from Fey giants and HP curse from Barovia Shadows.
It's not ideal to turtle up all the time; eliminates all your melee agro and pretty much ensures even threat-80 DPS will yank it away from you.
Labrythine's Salt is amazing for quest tanking when combined with SDK chains or other AE. It helps keep things facing you rather than crawling around behind and facing every which way. The buff is great for boss/raid tanking, too. IMHO, it's probably the best tanking weapon in game.