I would agree with you however I only play mage when someone wants an AoE DPS. And when your party consists of 4 mages it kind of indicates that it's a speed run. Speed runs need OP healers, OP DPS and of course an OP tank. An OP tank should have enough pattack to hold the malice for quite a while. Generally an OP tank will only lose aggro when the mob is already half death and by that point when the mob should die before it kills the mage.
I main tank also, but will play different classes depending on what the party needs. I have 13k pattack, 46% eva and 8.8k def. I can pull multiple mobs and rush, I've had a party where we had 1 illu, 1 tank, 1 solo healer and 5 mages. These mages had 22-25k mattack each and if they were cast speed they had around 1k of it and all of them had 1k-1.4k mcrit rate. My stats nowhere near touch that but I held aggro. And they weren't like me, I wait for the tank, they were the rushing kind I had to race them to the mobs. My tank isn't OP by any stretch, I don't have +6 gear, I have no gems at all, but I get by. In that party I was talking about to be quite frank I was more scared of that illusionist. That illusionist had ridiculous stats and on bosses I had to provoke a lot to make sure the boss didn't eat them, because that deadly icicle was dangerous.
Maybe it's just me, but I rarely find a mage who can pull aggro off me consistently and if they do, I find it as a challenge, I switch my gear around, I start animation cancelling more, I ask them to cast elemental guardian on me and we have a competition in malice. I'm just a competitive person and trials are so boring without a little competition or chaos.
If I'm playing a mage and the tank doesn't want to play fight over the malice, they can stop asking me to be an AoE DPS. I personally don't mind dying all the time, but every tank I meet takes it as me trying to make their life miserable just because I play mage with the intention of dealing damage.