It might be more interesting to have an effect which allows Entrust to be used five times in succession, but prevents self-targeted Indi- spells and any Geo- spells for a while. Entrust spells are weaker since they calculate potency based on the target's equipment rather than the caster's, so it would be trading two big effects for five small ones.

Geomancer's real problem, though, is it just... doesn't have a whole lot to do. It can use elemental magic, but not as well as Black Mage and Scholar. Free nuking just isn't a big thing these days, if you're casting you're expecting to magic burst... but the diminishing returns on magic bursts means you want to actively discourage any but your best caster from doing them. A job trait that prevents spells from counting toward the penalty on successive magic bursts might make Geomancer a more appealing option for fights which need more magic damage.