I'm assuming you mean "capped", since this guy is "caped":

Btu there's no cap for avoidance as far as I'm aware. Well, theoretically there is if you can get to 102.4% combined dodge/parry/miss, but I'm fairly certain that's impossible with current gear and DR.
If you're block-capped and the Libram procs, all that'll happen is that some of your block rating will be effectively wasted for the duration of the proc.[/quote]
LOL i like the pic. and yeah I ment Capped
But hitting 102.4 is not impossible. The macros out are damn close to showing the correct "Block Cap" Currently im sitting at around 103.88% avoidance according to
/run ChatFrame1:AddMessage(format("Unhittable at 102.4%% - you have %.2f%%", GetDodgeChance() + GetBlockChance() + GetParryChance() + 5 + 1/(0.0625 + 0.956/(GetCombatRating(CR_DEFENSE_SKILL)/4.91850*0.04))))
Which i pulled off these forms which if i remember correctly was dived from a thread on Elitis Jerks. Im thinking the Libram of STR is an awesome Addition to a threat gear set while Libram of DOdge is nice for bosses that Hit hard as all hell. Right now though With me not in a raiding guild with mininmal time to raid Im thinking T9.25 shoulders and gloves are the way to go for the 2 pice bonus to be running 2 pice t8.5 and 2 pice t9.25
Again its all depend on what u want to do. Ive seen both librams in use by tanks and the One using the Libram o Str Liked it alot more then the one useing the dodge one. Yet its all dependent on what kinda of tank you are and what u THink might help. Personally Im still using the LOO because im too cheep or lazy to upgrade.
Also Ragingsoul on the comment of the BV and AP from Libram o Str
I think that no matter if ur "Capped" the BV is nice because in turn it turns into to more migidation. Insted of only blocking 1500 dmg you might get leys say 1656 blocked dmg which means thats 1.6k less hp u lose and one less heal the healer needs to throw at you to conserv its mana on lets say General Vajax.
on final not this is only my thoughts. Im kinda rusty since i recently started playing again so maybe i can get one of the old timers to confirm or shoot down what i just said