First of all, doing damage is against the core and class identity for tanks. You are playing a dps to do damage, a healer to heal and a tank to tank. That is the reason people play tanks and it should be the primary reason to play a tank. If E5S and E6S are able to be solotanks then that is just fine as well. I see no problem with that. People that want to do damage can just roll dps. Finally if SE wants both tanks to perform their intended role (ie tank) they can just add more adds, 2 bosses in the encounter, or force tank swapping with debuffs like they did in the past.

Besides, if we follow what you say and increase tank damage (without decreasing dps damage) and then increase the dps checks (to offset), that will just make savage raids harder and we will end up with Alexander all over again where it almost killed raiding because people couldn't clear A3S. To make it work properly, the devs to do a ton of extra work to properly adjust the dps checks. And all that would be just in order to get tanks do more damage and feel like dps, which they shouldn't be in the first place. It's a different type in the trinity. As for people that want to have more fun because they want to see bigger number they can just play a dps class.

The current state of tanking is what it is because they simplified tanks. Tanks stances are gone, the defensive kit is pretty much the same across all tanks, etc. And they did that in the name of "balance". After HW tanks have just been getting simpler and simpler. As a result tanks are now boring and noone likes them. Giving them more damage will not solve this fundamental problem. If they wanted to make tanks more accessible they could just make one or two simple (like PLD used to be).