In what world is source patching the only form of patching?
Ultimately, it is pretty much the only form of patching - veyr few people still do direct hex-editing these days...
Windows Update is two clicks and forget.
Ah. So getting someopne else to do your pathcing is easy. Well, it's just as easy in any environment where you can pull down someone else's code. That's my "at best, as easy to patch as Heartbleed" comment - if all you're doing is pulling down someone else's binaries, there is no difference whatsoever in ease of correction (thus proving the original statement of the SChannel bug being "[e]asier to patch in most cases" entirely incorrect).
But if you don't *have* someone else's binaries, Heartbleed is still trivial to patch, whereas SChannel is not. Thus proving the original statement of the SChannel bug being "[e]asier to patch in most cases" entirely incorrect.
If you ever look into it, I think you'll find that building a copy of DD-WRT is significantly more painful than changing one line of code, despite having the source. Then come back about how trivial it is.
Got a patch for Windows XP? Nope, of course you haven't. Patching is much harder if you get no support from upstream. But if you've got an old copy of - as per your example - DD-WRT with the Heartbleed bug, you can still patch it...