This is my take. ESO PvP population can be divided in two groups: players that create builds and general players. Players that create builds, wich later on will spread like a virus thanks to youtube or discord are a miority. These creative players adapt to the game, look for answers and come up with some. The Tank meta is a result of creative players trying to deal with lag.
If you were to run any high damage/low resist setup, you will find yourself being destroyed by a small number of casual players because often your skills will get an increased global cooldown, or you'll get the bar swap bug, or the sprint bug, or the infinite break free animation. All caused by the same issue: performance.
The only way to make yourself a few seconds more survivable in those scenarios, wich are everyday scenarios, is to build tanky. The game engine will always privilege movement and control of your toon over skill usage. So performance heavily impacts skill usage, but even on hard lag you will still be able to hold block, move, and even dodge sometimes. So the best way to deal with that is to have a very resistant toon. The whole meta switched in that direction not because players enjoy being permablockers or healbots, but because its the only sad way left to survive in a everytime less skill based bad performance environment.