Honey boo boo says that the problem with deoxys-s is that it was unpredictable. You didn't know if it was offensive or a suicide lead and sometimes that would cost you your spinner or magic bouncer. Garchomp could run about 2-3 other sets, but SV just made it easy to abuse one to absurd levels. Blaziken actually had some unpredictability because before it was banned, people started abusing special sets to nail its usual counters/checks, like slowbro and hippowdon. Predictability is actual a valid argument b/c unlike the ubers mentioned above, Tornadus-t doesn't have too many other viable methods to get past its counters or screw over your main game plan.
this is already the worst gimmick account i've ever seen
deoxys-s in bw1 was banned for its suicide lead capabilities and the fact that the lo sweeper set helps eliminate speed tiers and styles of play. i never met anyone who thought the actual problem with deoxys-s was its "unpredictability"
chomp can run scarf cb sdlo sdyache etc, but the problem was universally sand veil, and not its unpredictability. i mean chomps unbanned now and no ones complaining...
blaziken was banned once again because of its power and metagame decimation, pretty much forcing you to run a slowbro or azumarrill or w/e obscure answer. can it run different sets? yes, but the problem was once again not influenced by unpredictability.
Tornadus-t btw, runs a pretty effective flying gem acrobatics set for what it's worth, one that is actually extremely good outside of rain because of how useful regenerator + taunt + strong flying attack is. but im not complaining about the unpredictable tornadus-t...my issue is with his speed and power and influence on the meta with regen, fast uturn, great spam attack in hurricane, and the problems most of the meta have against a tornadus-t. it has counters but many of them either arent effective or they lose overtime because of regenerator keeping tornadus-t alive.