I hate to say it, but there's no reason to run Ingrain. 1/16 HP per turn is not worth a moveslot and a wasted turn in battle, during which your opponent could be switching to a counter or boosting in your face. Leech Seed is better than Ingrain, but even then, Trevenant is outclassed as a sub-seeder by Gourgeist and most other Grass-types.
The same goes for Phantom Force, which is a huge "please set up on me!" flag for your opponent. Seriously, Trevenant has NO use for Phantom Force at all, because he has Shadow Claw (I'm sure I already said that in this thread somewhere).
Beyond the OP sets, the only set that might have potential is the Power-Up punching set in the lower tiers.
So you don't think the extra turn where your healing and not getting hit is worth it? or that fact that it goes through protect/detect/kings shield? I'm not trying to argue you probably know best I'm just asking.