I'm running Savage Tide, and I've made it clear that I will let the dice do the talking. No cutting in on the group's behalf.
So now, the group is always on edge. They know that they can screw up, and even in simple fights (4 PCs vs. a CR 2 construct that didn't have much damage capability, for example) and the group is on the edge of its seat.
I really like this form of play - play the monsters exactly as smart as they should be played (so the construct, for example, just attacked a random foe, whereas the crossbowmen in an earlier combat focused their fire on the only available spellcaster, until the goliath got on board the deck of their ship; then they all tried to kill him).
All this being said, I have cut in once to save a PC's hide. The Goliath was at 2 hit points when he was attacked by a very nasty little critter that knocked him all the way down to -10 hp. I knew that, by the rules, the character was dead for a few reasons - 1) -10 means you're dead, and 2) even if it didn't, the cleric was too far away to reach the character in one round.
So, I pretended that I thought -11 was dead, and -10 was that you were on the VERGE of death (pretending you don't know the rules to help a PC is always okay, if you ask me), and I fudged things a bit by letting the cleric make a check of some sort (Balance/Climb?) to get to the dying goliath in time. Turns out it wasn't necessary, as the goliath stabilized, but still.