Bahh 1 more thing before I go to sleep haha,
Mentioning upping to 6 from 4, I've thought about this as well, but I love grouping with other players - it's half the fun in the game. At the same time playing 6 ( and this is something that was mentioned a ton when I was first researching on here) is that if you do build a 6 man group. It can be "perfect" and it is a LOT easier to find the synergy your looking for. Taking that team as you suggested and adding a Illusionist and a secondary healer.. your golden. It's pretty much perfect, you just can't make perfect groups like that normally - though if some 80 boss fight requires some additional attention it can be quite hard, but perhaps the synergy of the group can just surpass that point.