Trick Arrow is, overall, probably the weakest of the buff/debuff sets. It isn't bad but it's not as good as, for example, Dark.
For the specific combo of Demon/TA it's probably going to be ok, but not great. Personally I'd prefer TA paired with a more ranged primary since that makes Glue Arrow more useful (keeping enemies out of melee rather than just being a recharge debuff). On the plus side the recharge debuff will stack with similar debuffs from the demon prince which should help and between Trick Arrow and the Demon Prince you've got a decent amount of control.
I expect it'll be a long, hard slog to get to 26 (and the demon prince) but should get better after that. You'll get a lot of damage (since TA is a pretty good damage booster) the issue is staying alive. I suspect you'll find the best routine is to hit a spawn with Poison Gas Arrow (sleeping and debuffing them) then send in the Demon Prince and a Glue Arrow to slow them down while you set about killing them.
SO I started a MM Demon/TA and thought it would be a nice concept. But I was teamed up last night and was told that TA is a terrible power set for MM. Is it that bad? I'm just saying over all. The friend I was teamed with has played more MM than i have and pointed out no heal, no rez, no Buffs so I'm not sure he's wrong. I don't mind if it's not uber, but if it's terrible than I'd rather find out now than in 30 lvls.
Charles