In my experience, uncertainty over timing is a huge balancing factor for the powerful round per level buffs. If the DM keeps the players guessing when the big combats will occur, the PCs will either have to hold them tight or risk wasting the spells. If you want to spend the first 2-3 rounds of combat making yourself an unstoppable killing machine, I am sure your dead allies will be very impressed.
In a recent battle in one camapign I play in, we were making a sortie into G2. The place is crawling with Frost Giants. We know it. They know we are coming.
The Cleric was planning on the Divine Power + Righteous Might trick. He never pulled the trigger. Either the immediate opposition was so weak that the regular fighters could take 'em out easily themselves, or the opposition was so brutally violent that the fighters were begging for healing at the end of round 1.
The Cleric just plain gave up on the DP+RM tactic. Buffs were too slow. Better to unload a spell with a real immediate effect like Hold Monster, Greater Command, or healing.
BTW, a DM can also slow down the pace to similar effect. Wall spells, fogs, triggered partial collapses, traps, escape spells can all be used to good effect by the bad guys. If you tempt the party to hurry because of their spells, it may also cause the party to partially split up if their travel speeds are different -- that can force the party to change its game plan if even for a round or two.