Best class to complement an assassin?

My friend is making a republic assasin and I am wondering what are good combos? We have a lot of experience of 2vX'ing in many MMO's and this obviosly means we are pvp-focused with 2manning whatever pve content we can.

I am making a sentinel because with all of our self/group healing we should be fine in the small skirmishes we often find ourselves in. However, would I be better rolling a 'dps healer' or should we just find and recruit a non derpoid healer? If thats impossible, which is seems to be, how well will sent/assasin do at endgame roaming?

He said he will be 'tank spec' idk but Im going dot spec on my sentinel for the healing buffs and sustainer damage/lockouits to kill squishies.

Hes a shadow. whatever.