Deployment Tactics is strictly a mitigation cooldown. Fey Illumination is not. It's as simple as that. Otherwise I'd have taken Dissipation into account too.
But even then, it still doesn't change the situation of A.Benefic being miles above Adlo regarding single target shields, and Deployment Tactics giving the edge to the SCH in terms of AoE shielding. And notice how a Succor buffed by Fey Illum is still slightly below a simple A.Helios. Something else to consider is that using a pet skill is one of the most frustrating thing to deal with, and that's something to take into account when talking about Fey Illum.
So, while it's true that SCH have more potential tools for buffing its shields than the AST, their long cooldowns and weak multiplier don't really make that much of a difference. Dissipation will still be used mainly for its stacks reset effect, and Fey Illum will still be used for... well, simply giving you and your healing partner an easier time dealing with something, but not exclusively shielding people.
Again, I'm not saying these buffs are useless or anything like that. But the shielding aspect of the two jobs are mostly unaffected by them.
