Just in case, some very simple Raid 101 tips:
For Attack:
- It’s about trying to limit the mana recharge of your foes, and trying to get your specials up as soon as possible (within the bounds that the tile layout provides). Focus on taking out a single enemy to free up a gap, and look to expand that gap. This allows you to deliberately miss to charge your mana faster without charging them.
- High damage single target heroes in attack team do better than AoE. Also need to focus on using heroes with fast (or at worst average) mana recharge. Slow is too slow and your guy is likely to get taken out before he can use his special skill.
- Try concentrate on vertical tile attack rather than horizontal to stop charging up too many opponents’ mana at the same time.
- You really should play with someone who strips enemy buffs (Sonia; Caedmon; etc), and concentrate on charging their mana quickly. You can’t let opposing team keep their buffs up too long without serious danger. A debuff stripper on your team also really helps (Rigard, etc).
- If all else fails and you feel you have a strong team but are still getting frustrated, drop cups to face easier opponents. That way you at least can still fill your Hero chest without too much frustration. (Plenty of posts about dropping cups… but see here for a post in which I explain my method to keep my conscience clear).
For Defense:
- Team position is important. Put your healers and tanks (high health/defense) in central slots. They take more heat in the attack and will charge mana faster. Glass cannons to the sides.
- Defence teams are colour agnostic, so choose your strongest combination rather than needing to maintain a balance of colours.
- Attributes that are strong in attack are not necessarily also strong in defence, so you need to consider different teams. Quite a few posts in the board on which heroes are best for which role.
Quite a few ‘noob’ points there. If you’re already employing all these and are still getting frustrated, then I guess your only real options are to not play raids, or to drop cups. 
Good luck!