The question is does a very good lure at the beginning of the game deserve a ban?
i think thats the wrong question to ask to be completely honest. the real question is "is this a
fair lure" which by that i mean, sure, it IS a lure, but its a special lure that can lure for 5 different mons. say, for example,scarf illusion ttar is paired up with sheer force landorus, and a brave bird skarm. ttar can choose to either eliminate the opponents latios if it so chooses to do so, HOWEVER, it can also lure in the heatran on illusion with skarm, and help with ITS sweep too. i feel the problem with illusion is that allthough its no better a lure then most others, its that for ONE pokemon, its "Lure" can revolve around your entire teams normal checks. and not just 1 or 2 mons say, gale skarm has trouble with. sure, fairness doesn't matter as much in a competative game, but this is pretty much a "Shadow tag" situation as shadow tag was banworthy because it removes a healthy aspect of the game, illusion is suspect because under "worse case scenario" illusion is impossible to predict and can cost people games due to such.
to add onto this, although stealth rocks is a common sight, i hardly consider it worth a mention in terms of "is it broken". this is like arguing that Ho-oh would be okay in OU, because stealth rocks pressures it even with regenerator in its disposal. this is why most people don't take into account of "if its SR weak" when coming to bans and unbans, enless such measures stop it 24/7. illusion doesnt care about stealth rocks even IF its neutral to it, because enless your specificly looking at the percentages of damage, its quite easy to not notice "oh, why did that breloom take normal damage from stealth rocks" especially in that case, since nve and neutral to sr is actually a pretty negligible difference. on top of this, this meta also has magic bounce, priority defoggers, and on top of most pokemon being "neutral" to stealth rock, its really not a problem for illusion half the time, especially since although SR is commonly thrown around, its also commonly removed asap. stealth rocks is a very situational argument to pull, as allthough you CAN set them up, you cannot GUARENTEE their addition, therefore in a "worse case scenario" stealth rocks should NOT be up when arguing a point. when you argue to ban something, you HAVE to bring up the "worse case scenario". in which this case, stealth rocks are NOT up. this is how OU, UU, RU, NU, and most OMs work, and we too, follow this logic. SR is calculated for kills, and its not for stuff like illusion. that is because "worse case scenario" HAS to be brought up when arguing. you cant say "well stealth rocks helps you find them" because then i can just say "well, i got gale wings defog. so my illusion is in without stealth rocks up, what now". on top of that, even then, this argument doesnt work 100% as is, as both pokemon i mentioned are both neutral to rocks. which means you will be none the wiser until its too late even IF you get them up.
now, personally, ive been using illusion with dual sheer force lando/thundy (lmao landos still a damn good Sheer forcer) and ill admit, i much prefer adaptability ttar over illusion, but id be lying if i didn't say i've got so many sweeps just because people lose their checks to the duo early since ttar smacks them. personally, i'm inclined to ban it now, because albeit its very very slim in my eyes, i feel its broken due to my above statement along with what others have stated.
(wow, it feels good to argue without attacking people due to them attacking my opinions/acting condecending. i should do this more lmao)