In the past I have done both CoA (excluding last boss) and all of karnors with a group of 3 (pally / mystic / swash) so 4 will be easy street - been using 6 for a while now

You should be ok in Voes for some of the bosses (be slow though) but may find it difficult in maidens (the first boss mainly - i.e., old man whatshisface and the bomb...)

The team you have selected is fine - be some nice dps and aoe

I have to ask - why karnors? 4 x 80s will whip around that place at a furious pace and honestly - each boss has a pretty small loot table so you will be seeing the same stuff all the time - suppose you could get the odd low level master if that's what you after - and, some of the collection stuff does sell pretty well too