It's not a problem if you take BS and -not- use Parry. If it doesn't fit, it doesn't fit. You still have the awesomeness of Head Splitter and Disembowel, two very strong attacks. Or just keep Parry on hand for it's speed and to combat defense debuffs... Overkill isn't always bad. Additionally, the defense softcap is higher in post-50 content, such as Incarnate Trials. Food for thought.
My wife runs a BS/SR, but doesn't use Parry. Build for the Headsplitter > Hack > Disembowel > Hack attack chain and revel in the awesome. As Necros said, Parry can still be useful in Incarnate content and it's also useful when exemplared below softcap.
I think it's a good leveling combination, as Parry keeps you alive before Super Reflexes kicks in. It turns a late-blooming secondary into an early-blooming one. I wouldn't IO it out for regular level 50 content as I feel there are better options at that point. But for incarnate content, the easy high defense could be quite useful, particularly on a budget build.
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Thanks guys, I knew the combo had to have some synergy or I wouldn't have made it.
That said...off to make a kat/stone brute. 
I have one thats pretty effective on a very cheap IO build without having to use parry sitting at around 50% def to all plus absolutely no end problems.
I was going through alts and when I got my BS/SR out and looked at her potential...the massive overkill in melee defense with Parry and the armor powers...I'm not sure the set makes much sense for my playstyle.
Why take BS if I'm not going to use Parry? Why take SR if I'm going to have Parry [or DA for that matter?]
[On my kat/wp I set her up usually to be one tap into the 40s, though now she's one tap capped and sloow.]
Does anyone run this AT? Does it make sense?