A new way of gym trolling
Look at this.
This guy does this in gyms all over the area.
It must be done using 2 accounts, as you can't add a pok unless you prestige it, and it's IMPOSSIBLE to prestige..
It's from my own team so I can't kick it, but every time I put a mon there (when another team kick it and i kick the other team), my mon gets kicked and soon later he arrives, and he must add 3 poks from 3 accounts and kick them after 3 first level are kicked so its just the blissy at 1000 prestige.
And on a similar discussion - i think putting a blissy first on a gym is a very bad idea - its unpreatigable..
My best mons sometime time out against these best blissys (2800-2900 vaps, 2800 drag, 2600 machamp ext..)
(Typos fix)

Answers
I haven't tried yet, but with the NEW movesets, I think Machamp should be able to fairly easily get through these high CP Blisseys since Machamp has much lower CP than Blissey so you can still net 500 Prestige...(You can get one with dodging in about 60-70 seconds give or take).
After you pass the lower CP wall if Blissey is there, you can use the rest of your team to get around 500+ per mon afterwards (like Rhydons, etc....as Machamp would have lowered your normal prestige gain).
At least this is from running tests in Pokebattler..but you must have the new moves Counter specifically and either of the fighting moves.