Hmm. Was just looking through the Warlock in a bit more detail and realized something I’d overlooked in the Invocations. Basically, each pact has an invocation which is so awesome that there’s pretty much no reason NOT to take it (Book of Ancient Secrets, Voice of the Chain Master and Thirsting Blade). Not a design choice I’m terribly happy with – it’d be cooler if those were baked into the pacts – but now that I’m aware of it, I may need to revise the Pact of iron to add a similarly “must have” invocation. Arguably, Unyielding Armor of the Void fills that niche, but I put that in just to allow AC to be a bit better at higher levels (and still comparable with mundane equipment).