Improved Leader of the pack vs defense rating capped

hi guys..got 2 issues here..

1. when we hit our bear def rating (142 def rating = 415 defense) meaning technically we are uncrittable by a level 70 mob or 73 bosses..so does putting 2 points in Improved Leader Of The Pack (where we have 100% chance to heal ourselves when we get crittaly hit by melee or range attack) does us any good or it just a waste-point spending there?
2. by hitting our def rate cap..does it really mean we are uncrittable aka immnue to crit or we still have a slight chance to be crit (either by mob or boss)? if the answer is YES then it will also answered my no.1 question above..

You always spec into Imp Leader of the pack no matter what feral spec you go.

Man a boss crit is far more than 4% of you HP regen, and talent is heal when you crit you (not the boss hit you).
Your group; rogue war etc... will be healed too when they crit (6s internal CD)

As they have already said, YOU HEAL WHEN YOU LAND A CRIT, not when you receive it.