Machinists of GAF, what do you do for solo heals? Apart from "don't stand in anything".
That's pretty much it for solo content. Bring a Chocobo with healing skills? In party content it's more Don't stand in anything, know where your healers and Eos/Selene are at all times. Don't be the jackass that always stands out of AOE healing range and dies to attrition (I am this jackass a lot.) Maybe be careful with B4B, but that'd be hypocritical because I pretty much pop it whenever and have faith.
If you know a big raid-wide AOE is going to come up and wreck your day (A3S phase 1 splashes can be particularly nasty since we'll get hit harder than most of the other squishy party members due to low HP and not great MDEF, although now that everyone's full i210 this is less of a thing), remember that Dismantle and Rend Mind are your friends that should totally be one button but aren't because this game sucks. They're only 5% reduction, and you have to know if the attack is physical or magical, but it's still 5% less damage to worry about. It's also nice to have handy for 6x splashes later in the fight, since that's a ton of potential damage and 5% over time can add up to a decent number.
Beyond that we have no method for getting HP back. Pots, I guess, but any content doing enough damage that HP is a concern is content you're probably using Dex pots on anyway.