Major Hint: Do not get sentinels if you are trying to get ridiculous combo. They will make you lag for about 3 seconds and slower your combo for that time. Otherwise your combo should be around 1-2k /sec combo.
IF YOU ARE HAVING TROUBLE WITH LEVEL 25...
1. Use a class 1 tank
2. Use two leech guns. You get healed 2 health every time you hit an enemy. You can basically just sit there shooting and let the bullets hit you. (4 gun points each)
3. Use a 5spreader gun. (3 gun points)
LEVEL 9 EPIC HELP
Problem: Blue Archers
Level 9 epic was the last one I did. What i did...have fully upgraded army (everything you are using) and have the skills shield. Have 400 mana using the mana altar before entering battle. Wait at your castle until you have 400 mana. Then, send your army forward all at once and when you get close to the archers, turn on shield giving you 20 secs unvulnarability. This will cost you 80 mana, and you should be able to keep using it until their castle is destroyed. Easy win. Good luck! Hope this helped.