Since my main was also inq (monster tactician), picking inflict solved my heal problem for Jaethal. And yes, you need to heal your tank from time to time, at least keep her topped up since natural 20s always hit (I'm looking at you double 20 rolling greater enraged owlbear like treant ). If you don't have a spontaneous divine caster, buy some (hundreds of) lesser scrolls and waste time casting them. Inflict wound potions are expensive, we need them moneys to build structures and appease our OCDs. Also Harrim can squeeze in some inflicts (especially the critical one at spell lvl4) for emergency casting.
Jaethal is worth all this fuss since she's immune to mind effects and poison (this is only important for earlier levels but nice anyway). No CC, no ironwill stacking, no event based fears locking her for 30 secs, just pure tank&spank.
Her tank build is pretty straightforward, take 7 lvls of tower shield specialist with all the necessary tank feats (dodge, combat exp, heavy armour focus , shield focus, imp unarmed and crane etc.) , then pick stalwart defender for 3 levels for uncanny dodge, and continue TSS for that juicy max dex bonus. Mithral plates are useless for TSS, since the tower shield also has +1 max dex bonus (are there mithral tower shields in the game? Havent found one yet). I made the mistake of leveling her inq to level 4 (since it gives +3 BAB after lvl1), thinking that lvl2 spells, improved regeneration and a bonus teamwork feat would be worth it but alas they proved lackluster. Pure TSS is the way to go. Her first level is wasted, but being immune to fear/confusion/laughter makes up for it.
One alternative is taking 6 levels of vivi for %75 crit reduction since you only get hit by natural 20's anyway and the extra AC can be obsolete. I just finished bloom and starting act3 now with 54 AC (buffed). If the AC/monster attack difference keeps up, then it's definetely a viable option rather than going 70 AC.