​According to Jeff Kaplan, Overwatch's balance isn't too far off from where it's should be. Most of the heroes are exactly where they should be, despite player opinions to the contrary. However, Jeff also admitted that both Roadhog and Mercy could use some attention in the future. 

Roadhog is the easiest hero of the two to examine. Since being shifted away from his one-shot playstyle, the 'Hog doesn't bring that much to the table. Sure, he's got better DPS than he did before, but without the ability to instagib enemy heroes, he's little more than a walking sack of health.

'Hog's hook is what defines the character, and I believe that any buffs Blizzard gives him should be in that direction. Reducing the cooldown on Roadhog's hook back down to six seconds is a reasonable direction to take with the character. Such a buff makes Roadhog more valuable to his team without making him overpowered.

Mercy is a more tricky proposition. The biggest issue with her kit is how little optimization she has - unlike Ana, who needs to land shots to heal, or Lucio, who needs to switch between speed boost and healing to succeed, Mercy just holds down left click while staying out of sight. Her ult has zero counter-play as well, which is a problem. 

I'm fine with Mercy keeping her "left click to heal" paradigm, but she needs something to optimize her heals as well. I'd personally suggest lowering her healing beam's power, but giving her a way to "pulse" the effect for vastly increased healing for a short period of time. It's a little like Lucio's healing boost, but since it's single-target the effect can be much larger. 

Resurrect is even harder to figure out. The ability right now gives Mercy the chance to swing a fight just by being in range of her dead team. Making Resurrect only apply to dead allies in line of sight would be a good change, but I'd also like to see a small delay on the ability - maybe 1-2 seconds - that notifies the enemy of where Mercy is and what she's doing.