I would say a shaman is the most durable, if you don't want a paladin healer.
Not sure that a Paladin would bring a whole lot to your team.

As 4x Pallies, you could bubble your healer several times.
Subject to Forbearance.
Blessing of Protection isn't everything, but it prevents a fair amount of physical damage.
The resistance totem (healing stream glyphed) overlaps with your resistance aura, each adding one extra resist and sharing two.
Tremor would be a second fear break for the team.

You'll likely want to macro Word of Glory for the healer.
Probably a round-robin effect, so you don't blow them all at once.
In 4.1.x they're putting a cooldown (20sec) on WoG for non-Holy pallies.
There is a glyph for it, where it heals half as much but then does the remainder over time; that would allow you to have them all use it whenever, and not be totally wasted.

I'd go shammy for the healer, if lots of healers were options for you.