Hi all! 
I just wanted to share some quick tips to help players who feel overwhelmed when playing against Mythic stacked teams.
- No killer weakness frontlines.
Avoid anything weak to killer moves for protect, Sleep, Toxic, Stun, Chrono etc and you will automatically create deadweight. Scarley, Shadowyrm, etc will all give you an instant advantage because they’ll do nothing. Obviously if you’re going all in on a sleep or poison strategy etc, then ignore this rule, but if you’re not, try to avoid adding unnecessary weaknesses and look for alternatives.
- Piercing.
Against the big scary whales, piercing is key!! 
It ignores defence. Much of their advantage will come from defence boosts, shields or just higher stats in general. If you have a load of piercing, it will level the playing field a bit more. Turn on the piercing filter and see what you have and build around that. Scary monsters like Vixenblade, Charybdia, cobalted XYZ, Bridlith etc are a lot less scary.
3. Use multiple combo enablers.
When you’re making a team that relies on synergy and combinations, consider having an enabler in both the frontline (in my case Jaguardian) AND in 5th (Arachnodrake). This puts the opponent in a difficult position because they can’t sit and do nothing to play for time and they can’t kill a monster like without playing into your hand anyway.
4. Monsters that work alone AND combine.
Synergy is generally when you’re combining 2 or more monsters to improve their output. There are plenty of monsters that offer this, but also work standalone too. For example if Suikensenshi, Jaguardian etc get knocked back or repulsed, they can still work alone and be effective elsewhere in the team. However combined, they’re even stronger. Don’t make the mistake of thinking you need to have one or the other. Monsters that are too situational can be easily knocked somewhere else in the team and cause problems.
5. Multi-lock mid games.
Generally speaking you want to use your mid game to regain control of the game. Spread your bets on this. Don’t feel like you have to go all in on sleep, stun or tokens etc. You might find that it’s more effective to mix it up. For example, if a stun absorber is up to 300+ secs, it’s out of the game. All you need is anything else to sleep and now it’s 2vs4. Throw in a shell here and there and it’s pretty much game over.
6. If you’re not going to spread purify and stun protection throughout the team, get creative and find an alternative!
For example, Arachno can use toxic thirst to wake up sleeping monsters or kill shells. The opponent wouldn’t expect it. Plume and Soral could pull back. Soral could sacrifice. Persephia could rebirth and so on.
I hope it helps!
Good luck
I actually had a different account before this one. It was F2P and built from scratch. Using that account, I became the first F2P player to get the rainbow icon (which was top 10 five times). Joint second player over all to get it. Over time I’ve created a ton of strats that have been taken on by a lot of players. Such as:
It was my first top 10 
. Since it seem like “I used myth to destroy myth” in your case.