You might be a bit confused here.
Block cap, aka 102.4%, is the amount of
combined dodge, miss, parry and block required in order to not take full damage from every incoming hit. Because a block is the last thing that can happen on an incoming hit before you take full damage from it, once you've reached that 102.4% number, any additional block rating is essentially wasted, though any increases to the other stats will still apply, though are subject to diminishing returns.
This does factor in your base percentages - somewhere in the neighborhoods of 6% miss, 15% dodge (w/ anticipation), 15% parry (/w deflection), and 10% block. Factor in Holy Shield as well for the extra 30% when it's up.
This also means that it's largely dependent on your gear. If you had no mitigation stats on your gear what-so-ever, you'd have a hell of a hard time reaching this cap, as you'd need to ensure that HS never drops... and you'd essentially need to be chain-proccing Redoubt as well. (Aside - is the maximum Block chance still 75%? I haven't heard anything otherwise...)
Because of DR, the best way to reach this block cap is to balance the stats on your gear. Looking at it, everything's just got pure defense on it, which is nice, but it doesn't help a whole lot when you start raiding. As your gear upgrades you'll find pieces that have more mitigation stats on it. When you start gemming and enchanting your gear, you'll get more mitigation then as well.
For an actual answer... check how much your numbers add up to, then figure out how much you'd need by looking at
this table. Suffice it to say that it's damn near impossible to get that much rating from gear alone, even without DR applied.
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Me: 15/15 Naxx-10, Arch-10, Sarth+0-10, Arch-25
