Since you gain the AF bonus, and Dps bonus after you hit the 5L0, as if you were level 51, I was wondering if the same bonus also applies to skills/spells.

So if I have a Pole Armsman, should i make it so that with items bonus and RR bonus i reach 51 in slash/crush/trust or is it completly useless ?

like: 36 + 11 + 4 = 50 @ rr4, then 51 @ rr5

or: 35 + 11 + 5 = 50 @ rr5 is enough?

also, in case the answer to my question would be: "yes, its useful to have 51 @ rr5", i ll ask: does it work with every skill, like stealth, etc. or just with some of them?

51 is the way to go regardless your RR.

Stealth "caps" at 50 in RvR because there are no higher players than 50.
So do poison because there is no poison at level 51.