I would suggest the Pally fullscreen on your main monitor and splitting the 2nd monitor into 4 equal sized windows.

Ideally you will be controlling all your fights from the Pally point of view. Controlling a melee character from your healer point of view will just lead to drug abuse and an early grave.

You will want to macro your healing so you don't have to look at the druid window at all.

In combat you want to try and control everything from your main point of view.

You will still need to click in all 4 clone windows to loot items or talk to NPCs or use your bank and vendors etc. So making one bigger than the others is not really beneficial.