The only two classes I really play in PvP are Bard and Paladin and I have to say that I didn't find Summoners to be an issue. Their burst is not to be underestimated to be sure, but it's very easily countered. The only issue I really had with them is their highly potent DoTs that lasted long after you fled the encounter where a healer was absent - DoTs that ticked so hard that they'd easily drain your HP on their own from 50% or more health unless purified. Granted, this is probably less of an issue in Feast, especially so with healers who know what they are doing, but I can't say that I imagine anyone who complained about their damage was anything but new to PvP.