As a main Summoner, I don't feel like I'm making that significant of a impact in terms of dps. Mainly because the DoT damage counters are lost in that pile of ally damage counters.

I feel that the Summoner pets are the real issue here. Besides Garuda's Contagion to extend the DoT timers and Titan's ability to play solo with, there almost have no synergy w/ the player. I don't know about other MMOs but I'll name the one I only know of: Guild Wars. The Ranger class in that game allows the player to call upon a pet to do battle with. The pet itself has no skills, all skills are commanded by the player. I can choose what I want my pet to do. Attack faster, chase someone down, silence, daze, hit harder, etc. I feel like an actual pet master w/ full control over what my pet does.

Here, I just sic my pet onto the enemy and leave it alone. Occasionally changing their locations and whatnot.