Having the ability to cancel animations would really ruin a very unique aspect of what Dark Souls combat is based around. The "canned" animations are there for a reason, and if you can't accept them or understand said reason, then Dark Souls is not the game for you. The time spent swinging your weapon does not make the game artificially "hard"; instead it removes the gameplay from being solely reflex-based.
The real reason why the Souls series has such a reputation for being "difficult" is because it's gameplay is not base entirely around reactions. An essential part of the challenge comes from something that a lot of gamers shy away from these days: KNOWLEDGE.
So this puts Dark Souls combat mechanics in this hybrid place, where the faster you can UNDERSTAND what an enemy is about to do in the next few seconds, the more time you have to REACT and take advantage. This is the crux of Dark Soul's challenge and it does not need to be changed.