I have always had a soft spot for summoners but unfortunately not in a necessarily positive light. When tanking dungeons, summoners always seem to get in my way more than anything. Partially its because they are using the wrong pet and also because they just don't put out any damage by either burst, sustained or DoT's. Do I ply a summoner? No. So I can't say with any experience about the class. But I have always bee very underwhelmed by them. They always seem to be overshadowed by the other DPS classes. They are not like other pet classes in MMO's from what I have seen.

Example
Please note I am not a WoW fanboy by any means. I played WotLK and a small bit of Cata before I lost interest. I am a MMO drifter usually so I have played many MMO's over the years.

I played a hunter up to level 82 in WoW. Both Beast master and Marksman were viable end game builds. By either buffing my pet to do great damage or Doing high Burst damage as a Marksman, I never felt useless.

Do I think summoners are useless? No. But I do think they could definitely use some love in a future patch.