Indeedee (F) is a good candidate. Doesn't have awesome raw speed or Prankster, but it can learn Light Screen and Reflect via TM and Heal Pulse as an egg move. Grimmsnarl is an alternative, it has Light Screen and Reflect+ Prankster, but I don't think it learns any moves that can heal an ally (it can learn Leech Life for itself though). Either one is nice, but if you want priority go with Grimmsnarl or for healing go with Indeedee (female, make sure it is female, if it's a male, it can't learn any of the moves I listed.) Indeedee isn't THAT slow, but Grimmsnarl is, but Grimmsnarl gets priority. Another Pokémon with Prankster is Meowstic (M) but it's a Grimmsnarl that is diffidently NOT Grimmsnarl.
So, I've found these are the best Pokémon for the job, though only Indeedee can learn a Healing move. Hope this helps!!! :)