Very interesting angle, doesn't simplify the squads so much but massively cuts down on save rolling. Why just the 11 and lower and not al the saves? Good job though!
Yes, that's the tradeoff: You get more consistent fights (As you're no longer affected by the luck of the saves), but you pick up the inherent weaknesses of Damage Reduction.
That's more just a fun ability, but I don't see how it's complex/confusing. Attack 2 different enemies, but you roll the attack die once and use the result for both attacks instead of rolling for each attack.