Stoneskin

[Simaril]

You don't need a particular strategy in Normal Mode, just avoid aoes and stand as far as you can from the middle during Geocrush.
Stoneskin or not, nothing changes.
I find really useful to cast Stoneskin on the tank before Mountain Buster in Titan Hard Mode, and I usually try to swiftcast Stoneskin on the tank each pull, but only when we are doing 10 min speedruns.
Until lv50 you don't need to worry that much about other than healing skills.

I understand your intent, but the reality of Duty Finder groups is that I can almost always make the groups better by doing a lot more than using the healing skills that I should need to (I mean this in general - not just Titan).

[YanDere]

I understand your intent, but the reality of Duty Finder groups is that I can almost always make the groups better by doing a lot more than using the healing skills that I should need to (I mean this in general - not just Titan).

Well, I think all pre-endgame content can just become worse, than just healing in a plain way.
It's just my opinion, but in Titan NM you just need to heal. No more. If you use Stoneskin you either won't get any benefits, or will get distracted from healing and let the tank die.
During Titan HM we use Stoneskin only before Mountain Buster, which is a skill that Titan lv34 doesn't have.
What I suggest is: just heal, you'll be fine.
But it is only my personal opinion, you can practise and see what you feel like doing.
Stoneskin is perfect just before pulling, and totally unnecessary (not even helping) after, in any pre-endgame content.