It is true that Dracula is random and unpredictable, but that is why you have to learn his attacks. It is possible to get two jumps in with three or four shots (Depending on how fast you can mash) before he attacks. After that, you just have to make sure you are far enough away for the three cherries, white balls, or moon. Any other attack can't touch you as easily.
Once you get the two protoplasm out you have to keep them at a distance. I prefer to shoot them separately when he is warping. I get 8 shots off on both of them before he comes back, hit him another 9 to 12 times, depending on firing speed and attack he chooses to use, then they speed up, shoot them back again, jump up and shoot him two or three times (Again, depending on speed) while keeping the protoplasm away between jumps and he's gone.
Every boss has a pattern, you just have to adapt. If you wish, I'll record a second battle against Dracula and post it on YouTube for all of you to see.