I'd like to see 5-man dungeons, with a slight caveat...

I came from wow with 5 man dungeons. I have to say I like the 4 man/8 man system better

5 man party would be better by splitting the DPS more evenly 1 Healer/1 Tank/1 Physical Ranged/1 Magical Ranged/1 Melee. Would also make sense since DPS usually gets disproportionately hit for queue times for being the largest category.