As I mentioned in my review, McCree is by far the most powerful character in all of Overwatch given that he is useful in almost every situation, but also utterly devastating to anyone that dares do such heinous acts like entering the same room as him.

Thankfully, it appears that the Overwatch developers have spotted the same issue as they have recently went on record saying that they would be bringing changes to the gun-slinger himself, but also D.VA who currently resides in that awkward middle-ground between a tank and a speedy assassin.

Here's what Geoff Goodman from the Overwatch team had to say about McCree:

"I've been watching McCree carefully since we've released. McCree's flashbang plays an important role in being a strong option against very fast/agile teams (tracers/genjis/etc). It is also a nice tool to prevent close range devastating abilities and ultimates such as Reaper's Death Blossom.

That said, its probably a bit too good at dealing damage to higher health targets such as Tanks and barriers. I don't have any concrete changes yet, but I'm going to be testing some things internally to see how he plays.

...

Right. I think I wasn't clear enough. By saying 'its probably a bit too good at dealing damage to higher health targets' I mean his flash/fan combo, not the flash itself. Fan is more likely to see changes than flash at this point."

This is exactly the sort of nerf I proposed as well given that it doesn't change McCree's ability to completely decimate any squishy flankers that might come near him, but it does impact his ability to drill through tanks within a single second. If this change goes through McCree will finally have his own set of counters without removing anything that's actually fun about the hero, and that is the sort of balance I would like to see from Overwatch.

As for D.VA, her case is a bit more complicated, as noted by Geoff Goodman again:

"D.Va's damage is definitely on the lower side, much like Winstons. They are this way for a similar reason: They are both very mobile and hard to kill. Every character in the game has strengths and weaknesses, its part of what makes the teamplay work well.

That said, I do think the is some room for some D.Va improvements, but these are unlikely to take the shape of increasing her damage output significantly.

...

Yes she gets taken down quickly if she is fighting multiple targets, unlike Winston/Reinhardt because of their barriers. When I say she is difficult to kill its speaking from a smaller skirmish standpoint, which she can usually set up due to her Flight ability.

There was a time, when she was first implemented, where she had more damage than she does now. The way that played out is that she would fly into someone's face, destroy them, and fly away. There was little that person could do because her mobility.

As I said I think she can use some help in other areas, but I don't have anything concrete yet. The goal is that she should be a viable aggressive initiation tank, much like Winston can be right now, rather than some sort of beefy flying assassin. So any changes will likely be helping her in that direction."

I've only recently started playing her seriously, an ironic statement given that all I do is spam the "WINKY FACE" voice clip, but from my point of view her issue is not the lack of damage, but the annoying slowdown the mech suffers when it begins to fire. I would wager that simply removing that penalty would make D.VA a lot more enjoyable to play, but also more effective as enemies couldn't just slowly waddle away from you while you get to watch all of your shots miss due to their wide spread.

Do bear in mind that none of these two heroes are guaranteed to receive changes in the near future, so if the competitive mode launches and they still haven't been nerfed/buffed please don't go and throw a tantrum on the Overwatch forums, that's how the World of Warcraft community managed to alienate all of the communicative developers.