It's not actually that bad a comp to have offensive heroes on defense. Pharah, 76, McCree... These are all characters who work very well on many maps at holding a point. Unlike Defensive heroes (whose use tends to be more specialized), Offensive heroes tend to be just generally effective selections in most situations.
Sorry dude, but I gotta 100% disagree. Yes, defensive heroes are specialized, for defense. So you know, they’re probably best at it.
On Attack/Defend maps, if both teams are comprised of mostly Offense classes, then the attacking team is simply going to be favored, since payloads move faster going forward, and on point capture, you only need to clear a point for a handful of seconds to capture it.
Offense characters are good at taking out enemies, which is useful, but
people tend to mistake for always being a good thing. Taking the enemy down doesn’t really matter much if they’re taking your team out just as quickly (which is what happens when everyone is offense). Defense characters are
good at area denial; staying alive and keeping enemies out, which is exactly what is needed on Defense; not people obsessed with getting kills.
Yes, one (maybe two) offense characters on a team are absolutely useful (even required), especially as counters to enemy offense heroes, but
if they’re really ALL so universally effective, then I ask you, what
even is the point of the defensive classes? If defense characters are ALL really only situationally effective, that’s indicative of a huge game balance problem.
What’s the point of even having a diverse set of classes, if it’s almost always most viable to 3+ Offense heroes? The answer to that question, is that it just isn’t.