I like the earth blessing for sacred mages, but isn't it almost useless on sacred troops? It seems like it would only help vs incredibly and unrealistically long battles or spammed fatigue spells.
1) Depends on the sacred.
2) No, not really. Fatigue racks up after just a few turns and can quickly become a problem. Fatigue destroys your defense skill long before you hit 100 and pass out. Staying fresh is always nice.
This, pretty much. Fatigue is what kills easier than almost anything in the game, and is one of the reasons that thugs/SCs that
aren't fatigue neutral (or better) are another way of saying "dead", most of the time. Pretty sure it also jacks up the chance of getting crit, though that may be a knock-on effect on the defense penalties.
There's a very,
very few amount of non-caster sacreds reinvig doesn't help a fair bit on, and they're mostly undead (and (almost?) all of the nations with sacred undead have sacred casters to some extent or another). It's less useful on low fatigue or out-of-combat fatigue neutral sacreds (and I can't recall if there's any nations that have those but not sacred casters, sooooo...), but still helpful, and means you can do a fair bit more with any sacred
indie mages you happen across, of which there are quite a lot.
Minor earth is basically the most versatile bless in the entire game, bar none, without exception. Just about everything benefits from it, and a lot of nations benefit a
lot from it. Add on that getting it means you have guaranteed access to dwarven hammers and, well...
Always minor earth. Always.