Where did you get your numbers, or did you just make them up, the limit breaks were put in so that no content would require them, but you could use them to make up for a mistake, or to speed up as you see fit. One reason tank and healer limit breaks aren't used as often is they take better timing to pull off to be useful, and most groups just wipe and start over if there is a major screw up. Most parties I have been in on Ultima hard mode use the tank limit break already, it can be useful on learning T4 for the last drops if your healers and tanks are having trouble managing 2 dreadnaughts, or on Garuda if you loose too many stones, or Garuda Extreme if party members are low health running into the spiny area in the twister>center transition.