I'm done with Titan.

[Fadigre]

try a quick instant cast the second you are outside of the plume, something that lands on the boss, it will force the server to recognize your new location

Honestly the best thing you can do from my experience is know when it's coming and start moving.
It's incredibly difficult to get out of a plume once it's already popped. Not saying it's impossible, I've done it plenty of times.
But don't expect to get away without being hit every single time.

Titan normally gets about two attacks in before he uses his next ability. You'll have to find out how many times you can cast betewen them. I'm gonna say just throw one spell out and then an instant cast so you're ready!

If you're healing, don't sweat it. Plumes never hit the person with enmity (unless somebody stands near them) and stops Titan attacking.