Your gear has to be at a certain minimum to clear content; after that it's skill that matters.

If you have 2800 HP it's going to be hard to clear Titan HM, because you won't survive post-heart stomps without SS + Adlo, and if both of your healers and casters have that much HP you won't be able to get them all up in time... But if you have that minimum HP met and run it with 5 DPS, you can clear it no problem with a group that can dodge.