The damage per hit or DPH of SA is moderate at best. Therefore, to be able to dish out crazy damage you will have to learn how to stick to the monster and consistently hit the weak spots and how to time your dodge to get to the next weak spot and keep hitting.
The X+A full burst is only worth it if you can hit the last boom on a weak spot since that's most of the damage from the burst. It's also not worth it to use full burst on tails as it (at least the last boom) doesn't do cutting damage. I facepalm every time someone does burst on tail while the monster is down... --- Nothing is true. Everything is permitted