You don't need a good team for the Battle Tower. But I guess I'll rate it anyways.
Your EV spreads are kind of random. Usually you'll want to invest the most in the stats you're going to use most. For example, with Alolan Ninetales, I would probably change the EV spread to 252 Spe/252 SpA/4 SpD. That way, you outspeed more and hit harder, at the cost of some Defense EVs, which are probably not as important as SpA and Speed anyways.
Alolan-Ninetales - Light Clay is better than Icy Rock for this set. Your other 2 pokemon don't benefit from hail, but they do benefit from Aurora Veil. Also, you probably want to change the EV spread to 252 Spe/252 SpA/4 SpD
Blissey - Leftovers is better than Silk Scarf. Silk Scarf doesn't really do much, whereas Leftovers give you gradual recovery. A better EV spread would be 252 HP/252 Def/4 SpD and a Bold Nature, since Blissey's defense is so bad, but can be redeemable because of its enormous HP stat if you invest enough EVs. Even so, Blissey can't take a physical fighting attack, so be wary of those. Toxic would most likely fit better than Psychic, since your team seems to be pretty stally and the NPCs at the Battle Tower don't switch out that often. Also, Blissey's Special Attack is really bad and not at all redeemable. Psychic isn't STAB and only has a 20% chance of lowering Special Defense with Serene Grace, which really is not that good.
Porygon2 - I would consider replacing either Blissey or Porygon2 because they're both normal and they both seem to be doing the same thing on your team. But assuming that you're keeping both, you should get rid of Speed Swap, because it's very situational. If you really care about outspeeding that much, you can just use Trick Room instead. Foul Play is usually better than Psyshock, because Porygon2's Special Attack stat is only decent, and I wouldn't recommend investing in it. Discharge/Ice Beam is better coverage but Foul Play/Ice Beam works better for me.
Anyways, like I said, you don't need a good team for the battle tower. If you want, you can just rent a team from the npc at the battle tower. His pokemon are neutral natured, but you can still easily get master ball with them.
