The lag is due to CCs using Thread.Sleep(someValue) or StyxWoW.SleepForLagDuration(). Both of these are not recommended at all to be used. (We use them internally in HB to ensure certain bugs don't occur, but we do so in very key spots that won't cause issues.)
Most CCs will sleep after changing targets, or any "I need to wait for some response from the server" type thing. This is generally fine for CombatBot, but not for RaidBot. RaidBot enforces HB to keep a frame "locked" (eg; stop the game from executing until something is finished doing what it needs to) to pick up the extra performance. If you're sleeping HB while WoW is locked, there's obviously going to be lag.
Lastly; if you're running on a seriously old PC, this isn't something for you to use. It does increase the frequency of everything inside the bot, so it will eat more CPU. But thats the point. The faster it runs, the better your DPS overall.