It's a different game to FFXI etc. and therefore has different dynamics. There are still cure spells, just not "white mages". Conjurer has Cure, Poisona, Raise etc. but also has Fire, Blizzard etc. as well. Sort of like a red mage but without a sword.

How do you play without an out-and-out white mage? Well, you heal pretty fast when you're not fighting, there are a couple of warrior abilities which allow players to gain HP back mid-fight (Bloodbath, Second Wind) and you can always just level up Conjurer to level 4 to get Cure and then switch back to another class and put Cure onto the action bar list. Such is the way of abilities in this game - you learn them in one class, you can use them in others too.

Having white mages will inevitably be a requirement for large parties though, that goes without saying. That's why I mentioned leveling both Conj and Thaum, although it should be noted that Thaum's spells aren't as white-magey as Conjurer's are. There is however Sacrifice (use own HP to replenish many other's HP in a Regen style), Ressurect (Raise for Thaum).