I pulled swimsuit Yuuki and Leo Sinon with my pulls would that help? My 4* include OSuna, OSLiz, Swimsuit Yuuki, Leo Sinon, White Knight Eugeo, and I also have 5* Kirito and 5* Asuna.
Hmm, based on this unit list, its theoretically possible, but its going to be really hard. Do you have any freebie 4* / 3* healers? The Free Rechka/Yuna/Earth Asuna are all pretty good for tower if you have them. Your units are great for DPS and ranking, I don't see many that can heal. Also I'm not sure on your gear status, if you want to climb to 100, all those units need 4* armor and accessories and at least R3 gatcha weapons, and you can't swap gear around in tower.
Still this is a marathon and not a sprint and you have plenty of time. Its going to take 3 tower events at minimum either way, so try to get to 60 for this one, and 100 for the other 2, and since we get them once a month (or more), you should have time to gear up accordingly.
Breaking down your units:
Self healing (2):
These 2 can probably clear 2 rounds each solo if you are careful. OS Liz is amazing for tower due to her tankiness since she can block just about everything without worrying about guard break. Bosses at high levels can still be a threat since they might get 2 or 3 shotted so you have to be careful.
No self heal (3):
- Swimsuit Yuuki
- Leo Sinon
- White Knight Eugeo
2 Water types and a Fire. Yuuki has a shield which will help a little. But you would want to pair them with a 3* healer to be safe (you can switch them in between stages to heal in peace) Each pair is probably good for another 2 stages each
5* (2):
No one knows how good or bad they are in Tower, but its more about survivability then DPS (S rank is 3 plus minutes for Lvl 100, and I took 10 minutes to be safe last time). They have stand by healing, so I would pair them with OS who can tank while the 5* heal. Probably good for the hard bosses.
Not going to lie, its going to be tough. You probably have 10 stages per rest point, so you can barely make it (assuming you have the healers). You'll need perfect execution so any failures/ deaths (no retry in tower, not even for MDs) means starting all over again. Your units mostly don't have self heal (since OS will probably be saved for bosses), so you need to concentrate for every stage. To figure out what that is like, try the hardest ALO story mission (on Hard mode) vs mobs you can access with one 4* + 3 * healer. Then fight the ranking Master +2 (damage taken and time doesn't really matter as long as you don't die). You'll need to do that 5 times consecutively XD.
Still like I said, you have time, aim to pull on banners with self healing. Tower events usually come with the immortal units I mentioned and they usually get 3 departures + elemental advantage, so if you manage to get 1, it makes your life much much easier. Also R5 armor is nice for ranking if you care about that, but the R4 armor is pretty crappy to be honest. If we are talking about OS Asuna, R5 is basically OS Armor + a few hundred ATK and 3% ATK battle skill, DEF wise its about the same. the R4 armor has less DEF than OS and no atk buffs, so its worse than OS in every way (except that the +MP works for everybody). So save those crystals and don't swap till you have 50 to get the R5