Lately, I've been feeling like combats in my 5e game have been taking too many rounds. Once the novelty of the situation is established, the fight eventually becomes a slog as the players grind away at the enemies' HP.
For example, the party (a rogue, a paladin, a warlock, and a sorcerer) came up against two champions and a wizard. They took out the wizard quickly, and then it was just a slugfest until the champions went down.
I could end some fights early by having monsters flee or surrender, but I've been thinking about simply cutting the HP of their enemies in half to make these fights go faster. I'm also considering increasing the enemies' damage output to balance the reduction in CR. Does anyone have experience in reducing enemy HP totals? Did it appreciably speed up your fights? Does it totally screw up the balance of the game?
I'd like to emphasize that I'm trying to reduce the total number of rounds in a combat, not the time that any individual round takes. Additionally, I'm not changing the PCs' HP, only the monsters', unless an answer thinks that that's also a good idea.