If you're talking about using lightning staff heavies on the adds - that's not a bug or a cheat. At best it's exploiting a legitimate benefit of lightning staff AoE damage to kill the boss quickly.
If you're talking about the top boss falling into that weird loop I've seen a few times - that's a bug or glitch - but not a cheat or exploit, since as far as I'm aware theres no known way to trigger it at will.
Either way there is nothing out of the realm of possibility in this week's top scores (on PS4 NA). Havent checked scores on other servers but I'd assume we'd have seen posts if they were crazy anomalous.
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As for the glitch / bug I alluded to above - I've seen on two separate occasions a situation where the top boss spawns as normal, and then when the boss moves to the center of the area to spawn the first set of adds - it casts it's AoE attack and then just seemingly stops - it remains completely motionless for the rest of the fight, and there are no adds or attacks, allowing you to simply sit there and burn it down like it was a target skelly.
The first time I saw this it just happened, no team members had died or done anything unusual - the second time I saw this one team member died in the boss's aoe prior to getting stuck in the loop. Both cases that I saw of this glitch were prior to patch 1.22 (iirc) - and neither featured team members doing anything specific or unusual to trigger it. In fact everyone in both cases were totally surprised and not fully understanding what was going on.
Pretty sure it's a known glitch, but again - afaik - there is no way to trigger or exploit it willfully.
It's sometimes only rumors and I need to be carefull with rumors, but i have heard that there is a tactic: no add sparn with the boss.
In this case, i don't care about the term (cheat / bug, ...), it's probably a problem to be solve really quickly, because the fight with or without add, it's really not the same.
The leaderboards in ESO for a very long time have been a joke.
I mean no disrespect to the top guilds as they're still some of the best players and damn good at what they do, but...
Generally when a cheat/bug/exploit has been found as soon as one guild uses it everyone else has had to in order to keep competitive. ZOS doesn't ban for very many things so bugs and exploits are more "mechanics" until fixed with leaderboard content.
@Turelus - EU PC Megaserver "Don't count on others for help. In the end each of us is in this alone. The survivors are those who know how to look out for themselves."