More than anything else I don't want to melt another computer. How about just giving us a button/switch in our system menu that turns off all other spell effects/cast/flashing epiletic light shows on the boss EXCEPT yours.
I loved 25 mans but the strain on my computer was too great to stay in a guild that was exclusive to them. Also as a tank/healer/dps its hard to explain what happened when your average graphics card has a heart attack 1 minute into the fight.
Maybe even an side feature to say except this character so you could only see healer effects (ex. Lightwell, Spirit Link Totem etc.)
An addon can't do this because it would mess with the Terms of Service but seriously if they really want to sell 25 mans to people they should give this a try.