I agree. Seiken Densetsu 3 is an awesome game, but as you say there is an annoying small delay before the attacks, and the most annoying thing is the difficulty (you have to spend too many hours grinding to level up, which is probably the worst about this game). The graphics, story and OST are probably the best of this game. I finished this game 15 years ago, but I used cheats with the ZSNES emulator because I was underleveled and I got bored of grinding.
Another thing that I loved of SD3 is that depending on the main hero you choose, you start in a different place with a different story, and each hero has a different ending too (the bad thing is that you need to complete the game at least twice to get the endings of all 6 heroes). There are other games using similar mechanics of several heroes, like "Live A Live" and "Treasure of the Rudras", both of them masterpieces too; in these two games you first complete several main stories, and in the end all heroes join for the last part of the game; that is one of the ideas that I wanted to include in the hybrid game of my dreams that I want to make (with more complex mechanics due to the puzzle part of Zelda games), but that will be after we finish Children of Solarus, which is my main priority.
EDIT: if by "sword of mana" you mean the GBA game, I did started to play it, but I never got motivated to finish it. Maybe I had already played too many RPGs, or maybe I was getting "old", XD.