I don't think Trick Arrow needs or should get a heal. You're using a frickin' bow and arrow. That doesn't heal, unless you're shooting suppository medical arrows.
But several sets don't get a heal, and are fine. Sonic Resonance, Force Fields, Cold Domination, etc. At MOST perhaps you could have a Triage Arrow that sets up a Triage Beacon (from Traps) at the target location. But keep in mind, that's useless for any fast-moving group, becuase no one stays near it for long.
If you want to be a healing archer, the Medicine tree is available, and is honestly a better solution for heals you can use even on teams that move, and top off people as needed.
I think efforts are far better placed in strengthening some of the early weak arrows.
Entangling Arrow - give it a small fire/toxic dot ("caustic"?) and would allow it to set off Oil Slick.
Flash Arrow - I agree the To-Hit debuff is not strong enough as is. I would be fine with a base 10% (or more!). Yes, it's an AE power, but Poison and Radiation get better -To Hit powers at comparable levels in their respective trees. If boosting the to-hit much above 10% would be considered too OP, perhaps add a strong -Range effect, so things have to try to get into melee range with you before they can attack. It wouldn't change much for a "Standard" team with tanks and scrappers and MM minions, but it would make a huge quality of life for anyone soloing if they could use Flash arrow and kite for some free hits.
Glue Arrow - I'd look at the -Recharge effect. I don't know what it is right now, but it should be right up there with Snow Storm for -Recharge. I don't know that it needs more than that, except perhaps a faster recharge. Mobs try hard to get OUT of the glue, meaning they move slowly and don't attack. This already mitigates a ton of damage / gives your team lots of free hits.
Poison Gas arrow - I think entirely reasonable to give it a -Regen comparable to Poison Gas Trap in Traps.