My personal opinion is that this jump has a difficulty of about 7/10 for an ally melee while under pressure if I were to rate it. It's not impossible to reach an EFC who's up there. Should FCs constantly be using it? No... However, you're still in range of any RDPS and with stacks you're going to be 1 shot by any real ranged DPS so this jump is really only useful for a few minutes before stacks reach a significant height.
In my opinion, 9/10 times if the person doing this jump lives longer than the other FC who's able to kite without stacks / LOS, chances are this jump will not change the outcome of the game in the slightest. The Ally FC should technically be LOSing the Horde offense and if he dies before 4-5 stacks (at which point, this Horde jump is more damaging than it is beneficial) then imo the jump has 0 advantage as it seems the Ally team is doomed to fail to begin with.
How many games do you see a horde offense even enter the ally base before 4-5 stacks? Very rarely do horde really organize any sizable offensive threat. This jump puts you at a huge disadvantage against ranged DPS so he's literally either going to be chopped by melee while losing ranged, or freecasted by ranged while being hard to reach by melee.
Personally this jump has more significant disadvantages than it has advantages which is why nobody ever uses it. I could see it being "broken" on a team with 0 ranged DPS, but if your team has 0 ranged DPS you're doomed to fail long before FCing comes into the equation.
Imo this jump really just shuts up feral druids and rogues... which let's get real.... are pretty cheap to begin with if you ask me.
I was in a game where this was being done and we were heavily underpowered on defense. We had 1 resto shammy and me as a ret pally helping to heal on D. Perhaps we had 1 monk or something but let's get real here, I did not think that we'd make it through a single assault. I remember switching to heartsong BAR so I could spam heal our shammy who's hp was dancing between 5%-20% for about 25 seconds. Had I not gotten off a hoj and had I not had heartsong, I would have been oom right before the heal that lasted the shammy through the ally assault. Our FC could have been in range and the only difference would have been that the damage would have been distributed throughout more players instead of just being done to our healer. If the ally couldn't kill a resto shammy with a retpally healer, I doubt anything serious would have happened to our 4k HP tank had he been more accessible. Just my opinion though.
I don't think this is something that should happen every game, however, in pugs I think it's quite fine if a FC wants to become a sitting duck to any ranged DPS. This doesn't apply to the twink cup IMO because nobody would be idiotic enough to use this in a serious premade against an organized team. If there were a LOS feature to this jump to ranged DPS, then this jump would be insanely cheap. However, there isn't so I don't see it as anything terribly game changing. Premades aren't an O / D strat any more... it's a glorified mid scrum with FCs as close to the cap whilst being in range of heals as possible. Unless something huge with the current meta is going to change the premade strat, I don't see any situation in a premade where this would be used but that's just me.