Like many people have already stated in this thread, Tanking is a lot more fun at lower gear levels, unless you're the type of tank who prefers pushing for larger numbers.
My first heroic KJ kill came on week 1 as a 905 ilv blood dk. It was the most fun i had as a tank since Krosus mythic. I know people are gonna eyeroll and say 'blood dk', but hey, having those perfect vamp bloods on each claws cast, having that blodo mirror up for large meteor soaks and adds or even on claws, and outhealing healers on the fight, all these things contribute to making it fun.
Then there's encounters like varimathras.
Tanking is also fun in m+, or rather, was fun early on. With the go-go-go mentality that causes more harm than good in a run, it's more an annoying chore than anything. Although, that's not the case if you have a dedicated group to do keys.