>>17195851Charizard, Pinsir and Gyarados, along with Mawile and Medicham are really good megas. But they wouldn't be as common as Luke even if it was banned.
Venusaur is so damn bulky because it's only weak to flying and (lol) psychic. Not only it's got a great natural bulk but it takes neutral damage from everything and has a bunch of useful resistances in water, fighting and electric. It has Synthesis in case you try to wear it down and Sleep Powder to cripple a pokemon of your team as it comes in into a poke it counters.