Triple paladins PVE - Possible!

Hello,

i´m leveling this Triple pallies Team and im finding them incredible fun to play and highly durable. So far i´ve cleared deadmines (lvl 20-22) and stockade (lvl 24-26) and haven´t died yet. I´m running keyclone + isboxer (gotta love isboxer... healing has become so much easier with grid). my team setup is 1 pally tank, 1 pally ret and 1 holy (kinda hybrid, cause he´s DPSing when healing is not necessary).

Basically i want to know if are there any enconters where a shaman would be necessary, because fear/sleep is an issue to me.

Oh, do you think i´ll lose any threat/tank ability rolling a DK? the dk would fit better for PVP, but not that much for PVE. i do plan running heroics on 80 (just need to PUG 2 dps to fill the group).

thank you.