Edit 2: I'm an idiot. Surprise Rounds only have one action allowed. I've been running them wrong.

I'm all for letting the players have fun, and do cool stuff.

But I'm running into a problem.

My players are making the combats too easy, by getting too many surprise rounds.

The level of damage my players can dish out can end a combat quickly if I follow the MM3 rules of monster design. My monsters however don't even get a chance to act or do anything some of the time.

The way they do it is by using bluff or stealth. We have a changeling in the group, and they set things up to lure enemies into traps.

Then the trap is set off, and they get a surprise round. I do everything I can, like sending out high wis creatures, with trained insight for example... and they still roll high enough bluff checks or stealth.

We had three encounters last night. Two of the encounters, the enemies couldn't do anything before they all died.

I want to get something out of this too. I designed these monsters they face to be interesting, to be challenging, and so on, and they circumvent it all and eliminate my enjoyment in the game.

They're having fun, but I'm not. I don't want to have to start breaking the rules and fudging rolls to get some fun. Its fundamentally dishonest to me.

What do I do?

Edit: I'll be doing a few things. I'm giving my monsters temporary health bonuses so they can last through a surprise round if they're surprised, and as well, since they ambushed a small group just outside the camp in broad daylight, the whole platoon is coming right at the besieged outpost, right the eff now. No time to plan or make preparations.