Let's get one thing straight: I don't hate Roobushin. I hate when any Pokemon, especially a popular one, is overhyped. Saying that it can sweep well put together teams ala Gen4 Garchomp is overhyping.
Despite similarities, I find that comparing it to Machamp isn't really useful.
Yeah, they play different roles so to speak. Their only similarities involve they have some bulk, they're Fighting-types, and threatening under certain conditions. That's about it.
Also, in case you didn't know, Payback has been slightly nerfed; it doesn't double against switch ins.
Ah okay, I got it mixed up. My mistake. What a dumb mechanic change; guess Stone Edge is better under most circumstances.
Healing with Drain Punch is far from reliable. There are too many low HP sweepers and Ghosts for that to really work. The situation you suggest is great for Roobushin, but as you acknowledged, it won't always be like that.
Low HP sweepers are usually susceptible to Mach Punch, so it's normally irrelevant. Drain Punch is mostly for Pokemon that hold higher HP (think of situations like Suicune coming in for a revenge kill, but I guess it could just Calm Mind or something. Vaporeon might be better example ?_?). Drain Punch is still okay under situations like this. I found it great with Iron Fist. With WiFi, I can't really speak. Probably wouldn't be
as bad, but definitely see the flaws since its health restoring depends on the enemy's HP. I guess I've had better luck with it. Then again, I'd throw Roobushin in after a Doryuuzu killed something, Bulk Up in case it felt cocky with an Earthquake, then Drain Punch it. Leftovers recovery helps, and DW can use Tension Tyranitar if they really hate Sandstorm (then again why deny Tyranitar a free SpD boost?) But yes, Drain Punch is better on higher HP targets. Not doubting that for a second.
Besides, Drain Punch I never saw as reliable. It's more or less a beneficial secondary effect that it has. It works better on tanky Pokemon than it does with some sweepers (and I stress some since we're not including Gengar for example).
As for Ghosts, I will concede that's a difficult trial for it, but it's a difficult trial for most Fighting-types anyway. It's a common problem; especially with Payback's nerf. But yes, that would stop a sweep.
If Roobushin is weakened, and trying to heal with DP, Gengar can come in and finish it off.
Most of the time, you start with Roobushin at full health. Best way to drag him in is after a revenge kill; primarily one that is physical. A lot of the Pokemon that I've at least seen sweep lategame with physical Pokemon (think Doryuuzu, Terakion, Garchomp). I've seen special sweepers of course, so I take caution with that and don't send Roobushin in obviously. Physical Pokemon that aren't resistant to Drain Punch is usually the best way to use it. Okay, you're right that it won't likely get you full HP, and that's fine. Most of the time I'm content with 50-75% HP range, since it will allow him to brace a Physical hit if it comes and SOME special hits (I'm thinking more from a Bulky Water). Drain Punch is used primarily because Hammer Arm sucks. I think we can agree on that. Is it a bad move? Absolutely not. Can it be unreliable? Yeah, I can agree it is somewhat unreliable under some circumstances.
Comparing once again, Drain Punch isn't as reliable as Dynamic Punch, which confuses all but Ghosts and Own Tempo Pokemon, forces switches allowing Subs, and discourages anything but said Pokemon from switching in on Machamp.
If we're playing the Sub game, Roobushin does something different. Instead, it threatens frail sweepers that are weak or neutral to Mach Punch and don't want to take a hit. Fearing this, they'll switch out and get a free Substitute. SubPuncher doesn't even use Drain Punch anyway, and I wouldn't expect it to. Confusion chances are pretty damn scary when Machamp is behind a Substitute, but Iron Fist Roobushin behind a Substitute is pretty damn scary. The big and bad Skarmory takes 73.1% - 86.2%. No way in hell is any Pokemon, barring a Ghost-type or maybe a resist like Cresselia, going to like Focus Punch. Then you have Mach Punch to finish it off after the Substitute could break (which it likely will).
It's difficult to even compare the two. They play similar, and play different at the same time. It neither hurts nor helps them aside from naming pros and cons with each other.
I think we can agree that Roobushin is a formidable threat yet it should not sweep a good team.
*Shrugs*. Who knows, the good team could still be behind a bad player, but we also don't know what a "good team" is. People are so overprepared for Doryuuzu that they aren't looking at a lot of special sweepers. They're glaring right at Roobushin in particular, and taking minor glances at Azumarill, Hitmontop, Breloom, etc. Good teams have Terakion, Sazandora, Lucario, Tyranitar, (maybe) Darkrai, Heatran, Empoleon once it's outside of a Substitute, and many other Pokemon. These are still good Pokemon, and they're on teams. I know I named mostly Pokemon that are weak to Mach Punch, but even those that are faster and are neutral to the attack likely won't enjoy it after being battered up. Gengar, Starmie? Yeah, okay, see it. That still doesn't degrade Roobushin's point, since you don't see Garchomp "sweeping" them either unless it's Scarved, and then you have the scenario of Gengar having Choice Scarf.
Sorry if I sound verbose, but my main point is that Roobushin sweeping is not exactly impossible, even behind some of the better built teams. Sweepers don't sweep on their own anyway; it requires teammates helping them out with the sweeper doing minor to nothing while waiting for key threats to being removed, then finding the right time to switch in. So long as the Pokemon doesn't resist or is immune to Fighting and it's a Physical Pokemon, chances are Roobushin can start setting up from there. It all depends on the situation. Even Garchomp needs key threats removed to sweep, and just like Roobushin it is susceptible to a revenge kill from faster Pokemon. The phrase "Pokemon X beats Pokemon Y", so to speak. And I'm not saying Roobushin sweeps better than Garchomp nor is it a sweeper so to speak. It is a tank that can heal itself with the opponent, then put the opponent under major pressure if they don't have key threats alive.
BTW That usage list means very little, and I don't expect Roobushin to be top 5 or even top 20 in BW OU. Okay, maybe top 20 due to it's ability to check TTar, who will always be a threat.
Like I am echoing, it all depends on the metagame flow. Will it be Top 5 forever? No, I doubt it will be so to speak. That does not mean that it is something to just toss aside, since now is the present and you're shooting too far in the future where we don't know what exactly will happen. DPP had its occasional shifts much like ADV had some of its shifts. The Top 5 and Top 10 fluctuated in DPP, and it likely could in B/W. Who knows really.
Predicting it out of the Top 20 might be a little too far below the standards. I doubt Doryuuzu and Tyranitar are ever going to die down unless they're banned for some apparent reason, and I don't see Terakion plummeting to the UU tier anytime soon. Balloon Terakion is also cool with Doryuuzu not being able to kill it in one shot and Terakion getting a free Rock Polish. Thing is, we're way too early in the metagame, and at best we're making predictions and pure theorymonning. That's all I'm stressing I guess.