I like how the OP names all of these 'crutches' yet claims Assault Rifles are balanced. Laughable.
When my rapid fire Vector with Deadeye can still frequently be beaten by a Remington R5 or an AK-12 in close range engagements that says it all about how 'balanced' Assault Rifles really are. But I digress:
- Deadeye. Clearly not a 'crutch' as it costs FIVE points to equip and only works effectively when you are on a streak. A risk/reward perk which functions as it should.
- Danger Close. Don't quite get the complaint about this. Costing a ridiculous four points is a burden enough. The only problem with this perk was always in acquaintance with C4 + Riot Shield, which shows how broken that setup was rather than the actual perk itself.
The only thing which can be considered a 'crutch' is the Thermal/Tracker sight as both encourageexceptionally lazy gameplay and highlight everything that has gone wrong with this franchise from around Black Ops 1/Modern Warfare 2.