So, I knew how to play BLM just fine and was playing it before the changes. It was fun working with the timer as a challenging aspect to it and I was in the "RIP BLM" camp.
But I've also been playing it since the changes in Mentor Roulette. It's actually not as bad as I thought. In retrospect, it makes you realize the timers were just an annoyance. The planning aspect is still there due to Leylines and the changes to Fire IV don't really change that it has a long cast time and requires you to consider a solution for movement such as: Polygot use, Paradox, Thunder, Triple Cast, etc.
They did explain their reasoning which is that they felt it wouldn't handle the new raid mechanics well.
I thought that BLM would still be rough in M8 despite the changes but I just did it today and it's really quite easy to play BLM in there. The population of BLMs has definitely exploded since the patch. Any dungeon I get often has another BLM in. I've been in trials and raids in Mentor Roulette with 3 BLMs even today... the BLM population has really exploded in a way I've never seen before.