In actuality, Winston's Tesla Cannon out damages a mercy heal without the boost. Let's look at the facts:
- Tesla Cannon deals 60-65 DPS
- Mercy's Caduceus heals 50 HPPS (hp per second)
- Mercy Caduceus boosts 30% extra damage
- Tesla Cannon deals 78-85 DPS when boosted
This means, in terms of outdamaging a healing Mercy, you are beating her:
- by about 10-15 DPS, without a boost
- by about 28 - 35 DPS with boost.
However, Tesla Cannon doesn't have infinite ammo, and has a reload time of 1.5 seconds. Which means that's roughly 75 extra hp that's getting filled on the enemy as you reload, and it takes 5 seconds to fully expend ammo. Which means that, 5 seconds x 10 - 15 DPS = net loss of 50-75, which is then promptly healed back up while you reload. So at this point, while you can outdamage the Mercy while she heals, it is instantly negated as soon as you spend time to reload.
Thus, the damage boost is enough to outdamage the other opponent as a Mercy heals them. However, note that it is still a moderate kill time of about 5-6 seconds, even with a boost, as:
- 50 HPS, for a total of 325 hp healed for 6.5 seconds
- 6.5 seconds is the full time for a Winston to expend his ammo, then reload completely, ready to fire again
- 390 - 425 DPS under boost for 5 seconds, then 1.5 seconds of reload downtime.
Which means that on average, assuming a perfect scenario:
Over a period of 6.5 seconds you only outdamage the mercy by about 65 - 100 damage, while under the effects of a boost.
Which means that, in your case of fighting against a reaper (250 hp), that it would still take you at least 3 cycles of the 6.5 second cycle noted above to fully outdamage the heal provided by the Mercy, and that's still a roughly 19.5 second kill. A very long TTK.
As Blueraja mentions below, this really only applies to pure health and health/shield heroes, like Reaper, Tracer, and Soldier 76, which means that against armored heroes you're not going to be able to out DPS them regardless if a boost is active or not.
Situation 1: McCree's lock-on delay for each player is increased proportional to the amount of effective health gained through Lucio's ult. Given that McCree is allowed to use his ult unhindered, you are correct in your assumption that Lucio's ult would do very little.
That said, the delay caused by Sound Barrier is likely to afford your team the time to either prevent him from going through with it or at least to find suitable cover.
Situation 2: It is exactly as you have said. In my experience, and as indicated by a player's account of his experience in this reddit post, increasing a player's effective health removes McCree's lock on effect; however, I am not sure if this resets the delay entirely or if it just increases the delay proportional to the health gained. Either way, it's worth investigation.
In short, Lucio's ult is very effective at countering Deadeye.
Best Answer
Ana does 80 dmg per shot, being able to shoot 1.1 shots a second. Ana has a potential of dealing 88 damage per second (assuming with infinite amount of shots). Lucio without "Amp it Up" does 12.5 healing per second. Amp it up healing does 40 per second.
Lets just use Lucio as an example. He has 200 health.
Killing Lucio would take 3 shots without amp it up. With Amp it Up, it would take about 4-5 shots since Amp it up would lasts 3 seconds long.
However your Biotic grenades allow you deny any heal your enemy can get from Lucio. So I'd say no, it's not useless.
Edit: There's a recent patch that came out for PC version for Ana that allows her to fire 20% faster and her clip can now hold 10 bullets instead of 8. So firing into a group of people with Lucio just got better
Source: http://www.polygon.com/2016/7/26/12291162/overwatch-patch-ana-buff-mccree-nerf-pc