Or because of it. Gameplay is a series of interactions of parts. Focusing on making things interesting and unique in and of themselves often has extremely "meh" results in action. Which is a big part of why I've never been bothered by games keeping core mechanics very streamlined and simple. It's a phenomenal way of keeping gameplay smooth, and in my experience complexity of the underlying mechanics isn't proportional to complexity of gameplay for the player, so I'd argue you're not in much danger there.

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I'd argue the Promethean's weird abilities in Halo 4 can sometimes exemplify this, too. More often than not, the fear of Watcher intervention just encourages people to slowly, boringly grind watchers down before engaging Knights. And the Prom Knight's teleporting (and associated invulnerability) seems to come across to many people as more random and annoying than a fun and exciting addition to tactics.

(Granted, these things might all be mediated somewhat by a reduction in other factors that contribute to the bullet-sponge image people have of Prometheans... speaking of which, why are these super-unique-special enemies so often bullet sponges?)