3x or 4x Shamans? Help!

Ok so my question is about wether or not to make 3 shamans or 4...

My reasoning is I want to use all my shamans as elemental so they all will just do the same stuff (yes I know elemental sucks now but I'm willing to weather the storm till hell freezes over). I am going to use them both for PVP and PVE, and the obvious advantage to using only 3 is I get a 3v3 team (though after thinking about it, it seems stupid and pointless) also with having 3 it leaves 2 spots open in my group for 2 healers or 1 tank and a healer. The concerns with only 3 is the lack of DPS...

After writing this I think I just answered my own question lol, but I'll finish it for the sake of arguement.

Now with 4 shamans I have only 1 concern and that is tanking instances, because it would seem practical to take a healer along. Now are there any reasons why 3 would be better than 4 or vice-versa?

im a 3 shaman boxer kill normal mobs in a flame shock-lava burst go, same with players 14k health and lower, i like it more but others will say differently

4 shamans, only need a tank for instances and you can play in the 5v5 arena bracket