Originally Posted by Jare
Dot kinda touched on it, but if you can't deal any damage, you're not going to have to soak any damage because you're not the prime target.
Amumu is a meh tank because he's basically a grenade. QR and then he's basically useless. Malphite's a meh tank because (imo) he does too much, he's more of a bruiser than anything. Sejuani and Leona are bad because they deal no damage. The other tanks fall into some spectrum of the other four I just mentioned.
Amumu is banned in ranked games pretty much 100% of the time, if people are so scared to even play against him then I'd say he's doing a pretty good job at "being a threat" like you said, except not necessarily by damage.
Leona DOES NOT deal no damage, if anything, she deals too much damage, seriously do you expect a character with ~5 secs of hard CC AND a 70 armor+MR steroid to also be dealing insane AoE damage too (reminder, she has 3 AoE abilities and a spammable single target)? Her base damage and her passive hurt A LOT already.