1) Ironically, summoner has the least to do, pet management is simple minded in this game.

2) Again, only summoner can do this, they have the least amount of skill. you can fit into a single hot bar. All other dps classes required 2 to 3. Usually 2.5 or it becomes too much of a cluster

3) DPS use light or medium armor, however there is shared disciple of war armor that can be used on any DoW and makes it look like a heavy. I think you have the wrong idea of a dps role. Glamor system.

Mechanic wise it's Healers > DPS > Tanks; in most content the DPS are responsible to handle mechanics and not tanks. Maximizing dps is a lot easier said than done.