I had a few ideas that might help BLM, it's basically a Buff that can only be applied to DPS however it's not a buff that helps the DPS rather it amplifies the BLM's elemental powers as long as the party member remains alive.

The idea with BLM is easily Fire, Ice, Thunder, Every 1 min and 30 second from when battle start you build up your Enochain, when you have had Enochain up for 1min and 30 seconds you can apply your first buff to a DPS.

Thunder could have 3 stages, Potency, Duration, Instance abilities that doesn't influence global Cooldown.

Ice would be Increased Blizzard IV charges, Freeze becomes a placed DoT and Instance MP recovery

Fire would be increased Fire III proc, Fire IV potency, Flare potency

The downside of course is in order to gain all 3 buffs you would need to have the buff up for a total of 1 min with the 2nd and 3rd tier being gained every 30 seconds but you also can't apply the next buff til you have had enochain up for another 1 min 30 seconds.

Now maybe it would make BLM to powerful but it could easily be said that you can't apply the buff to another BLM, it can only be applied to DPS, so you'll only be able to use all 3 inf 8 man trials and when using it you have to hope that the other 3 members stay alive since if they die or you die you lose the buff completely and have to rebuild it.

In my mind I feel this would allow BLM to remain the "selfish DPS" with it's own build up mechanic that relies heavily on the survival of the party.

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Another simpler idea is Triple Cast can reset when using Scathe, this would allow moments when BLM need to move but can still use Scathe and opportunity to gain a "free charge" of Triple Cast to use again while on the run rather than Scathe.