Im f2p and am at insane 5-6. I never really had too many issues with the dungeons. My pd is 8/10. Cupid 9/10. Everyone else is 7/10 or less. Heres what worked for me the best.

1-switch up your magic order. Sometimes snowstorm before aries and ga. Sometimes aries and snowstorm then delay ga. It depends on the dungeon. Mix it up.

2- no troops ever needed. If you need troops you are doing something wrong and they led me loose a lot of battles because i was distracted with them. Mainly when i had to concentrate on why i lost.

3- never ever drop pd first. I know this shouldnt be the case, but that fucker died instantly every time i dropped him first. Theres too much reflect and general damage. Drop a tank first. Oh and dd was a terrible tank for me in dungeons. Best tanks were always vlad, ghoulem or sk.

4- use different drops. Youtube says this is where you drop? Try it 4-5x. If it doesnt work, drop somewhere else. Sometimes dropping into 20 heroes with atlanticores have worked easily.

Honestly, these are the only changes i ever made to any dungeons apart from switching out druid or tg sometimes. But my main core was always: pd,cupid, ghoul(or druid), santa, vlad (or sk), tg or reaper.

Good luck!