Currently people are complaining about Trust system after 5.0 MSQ and it is understandable why it is a issue.
1) Deleveling the trust has made people see it as a loss of Progress even though 5.0 MSQ was only the Demo version of the Trust and Full version is unlocked after compelting 5.0.
2) Players can't use Trust for all MSQ Story dungeons in Post-5.0 because their leveling takes longer than the player's leveling to progress thus forcing players to constantly switch between different Jobs to keep a Balance of exp again for their Trust with their Character.
3) The Trust EXP gain is far slower than our character's EXP gain in Post-5.0.
4) MSQ Dungeons are currently the ONLY means to gain EXP for Trust Companions.
5) Trust is introduced to HELP Players level in MSQ Story dungeons and not for us to help them level up in MSQ Story Dungeons.
6) There is hardly any reward to get them into lvl 80 unless players wish to have a NPC group to help level their alt jobs or the title achievement.
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To resolve some of these issues certain things I believe needs to be added for certain issues to be resolved despite that it is possible they are preparing these thing already for 5.1 to 5.5 contents.
1) Allow Trust to also gain EXP from Enemy kills in Dungeons just like the Player with their Complete Dungeon EXP reward
2) have a Alternate means to gain EXP for Trust outside of MSQ story dungeons. Even include complete Weekly challenges that provide EXP to all Trust Companions.
3) Have something related to Trust Companion's levels such as Trust Companion Quests to provide a side content storyline that allows our WoL to get to know the characters a bit more during the time when they are just doing their own thing outside of MSQ events.
4) If possible treat Trust level separate from character level so players can use Trust for all MSQ content. What the Trust Level can become is a "Trust bond" level to determine the level of "Trust" the characters have with our character that leads to them unlocking stronger skills (or upgrade some of their skills) and provide Passive Bonuses between WoL and that character when they are in the same team.