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I have the same MBP as you and have had no problem at all with flash in Safari since upgrading to Yosemite .
 
I just upgraded through the App Store .
I know how to do a clean install on iPhone and iPad but have no idea how to do it on my MBP:confused:
A few years ago I did have a problem ,( I don't remember what it was ) and  care had me install the "Combo" .
 
Three things I will never install on my Mac:

1. Adobe Flash
2. Java
3. Google Chrome

A few years ago I purged my Mac of everything Flash and Java.
Flash and Java is irrelevant today. It's no longer needed.
 
So far my Mac has never had a problem playing most embedded videos. On occasions I do see a "missing plugin" on some videos but I ignore those. Safari and Firefox has a large library of extensions available so there is no reason to rid your Mac of Flash for good.
 
My Chrome has been lagging really hard ever since 10.10.2....scrolling takes longer to respond, and flash and html5 videos are choppy and skip frames. Don't know what's going on, except its google messing up as usual.

I have to resort to using firefox now. shudder
 
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