The only legendary summoner I have is Scarred Llama Mage (which I use a LOT). Being that I am only in Bronze, I don't see too many of the other legendary summoners.
Also, I don't have any monsters with the Trample ability (and don't tend to see them in my opponent's, either), so I don't pay much attention to the Stampede ruleset. I have played the Holy Protection on a few times, and I try to play a lot of smaller monsters when I get tht one (more monsters means more hits and more Devine Shields). The one that irratates me is when you get a Fog of War ruleset while playing a Sneak or Snipe quest.