In general I find PCE load times to be far more tolerable than, for example, a Playstation 1, 2, 3 or Portable.
There are good games for load time and bad ones, but an average game usually needs no more than 2 seconds plus seek time. The worst ones are anything with the Arcade Card. Filling up the thimble sized amount of RAM in the CDROM2 or SuperCDROM2 shouldn't take very long. I don't know WTF "DD" is but Dracula X should be only a couple of seconds. If it's longer than this, especially if it's inconsistently longer, you are probably having read issues.
If I were to allow my prejudices to speak for me, which I occaionally do, I'd suspect you are playing CDRs and your Duo needs glasses.