In pvp the squishieness depends on your healers spec, a priest is by no means squishy and nor is a druid whos swapping in and out of bear form to throw hots, and a shaman wiht 14k armor and an earthshield up is pretty strong.

its a strange combo, you said you had the 1 paladin 2 locks aready, so why not 2 priests, or a shaman and shadow priest?

2 aruras isnt going to be a great deal for your warlocks, a spell resist and concentraiton aura, but why not a spell resist totem and cocenctration, OR even better a PWF, Shadow Prot and kings = seriously high hp for the warlocks, warlock hp go up to about 12-15k and yes with the best pvp gear it really does get that high.

paladin + 4 priests is a great combo, the paladin is getting heals form VE, as well as mana from those heals and mana from VT.

I do think that if you put in the extra paladin he wont be doing alot more to the group compared to if it was a druid/shaman/priest. The extra warlock is understandable thats one more pet and with improved life drain you could get 3 corruptions 3 Curses 3 SL and a Shadow Ebrace all in all equaling 10 affliction debuffs, im not sure if drain life counts as a debuff as its not on the target before you cast the spell, or if the bonus is worked out before or during the cast, but you would still effectively have your Drain Life buffed by 40%

it has potential, if you were to main tank with your paladin in pve and heal with your shaman/druid/priest and then in arena main heal with paladin as prot and add the shaman/druid/priest into the dps team. Could work really well.