A healer should be dying to 1 single dps eventually. Not in 5 seconds, but it shouldn't be that a healer can survive a single dps forever. That's my opinion, and I'm fairly a lot of people think the same about this.
I don't really bother about 1v1, but I'm fairly sure it's impossible to kill a healer 1v1 now unless you can pull off some ridiculous burst, which not every spec has.
If healers actually went OOM versus a single, equally geared, dps (not instantly but eventually) then it would be balanced but since that never happens blanket silences are needed, and also since most healers dont have to expose their cast bar that enhances the flaw even more