Prior to reading your post, I figured my Mod Vice is not strong enough to defend against Cat 9 mobs, but using your logic, I should be fine, right?
To understand better and answer your question, you need to calculate Damage / Level of the creature.
Q: Why do I have trouble with this mob `Zombie Cat 09` that is level 46 when I am level 68 Evader?
A: The Annihilation Zombie has a very high heavy damage / level mob. It is 211 damage / 46 level = 4.587 dmg / lvl
To understand what that means, you need to calculate the Araneatrox Young dmg / lvl and compare it:
138 dmg / 52 level => 2.653
So the
Zombie Cat 09 vs.
Araneatrox Young damage output is 4.587 / 2.653 ~= about 73% higher damage output then a young spider.
Or in other words, for each zombie cat 9 on you it's like you have two young spiders hitting you at the same time.
Two zombies is going to be like 4 spiders. 3 zombies ~= 6 spiders
That means your tank needs to absorb all that damage, either from your HP buffer or armour absorption.
Add the lower miss rate on top of the high damage / level and you have a more deadly combo then your regular mob.
Your Evader helps and you will evade lots of damage, but the hit that go through will hurt a lot more because of the high dmg / lvl.
Basically, you will need to beef up your tank for the particular mob. Add more armour or increase your HP.
Hope that makes sense.
P.S. I think the level of Mayhem creatures do not follow the regular formula and might be hard-coded or relics from the past. The level is extremely underrated and should be about 70% higher then it is. e.g. Cat 09 should be L78 and Cat 10 should be ~=L140 to align with other mobs.