As far as I can tell, Magic Reflect no longer requires a cooldown once it wears off... you can just recast it immediately.
So, I logged in early in the morning around 5:30 EST. My character, who I think logged off with Magic Reflect in place, had no Buff/Debuff icon for it when I logged in at that time. But, if I tried to cast it, I got the "will not adhere to you" message. I lightning-ed myself a couple of times and tried to cast Magic Reflect again and it worked, immediately. No cooldown period, no cooldown icon, etc. Consistently for the next hour or so, I was able to re-apply Magic Reflect whenever it went down. Again, no cooldown period, no cooldown icon, etc. I logged on around 8:00pm EST, and I believe I saw the same thing. However, at some point thereafter, I got the cooldown icon and waiting period back. I'm calling ninja patch on this one. I'm 100% certain the cooldown timer was gone from 5:30 to 6:30, and pretty sure it was still gone in the early evening when I was logged in. If it was a character-specific bug that I somehow initiated, I'd sure love to know, but I don't see how that could be the case. I was shocked no one else was chiming in about it... especially all the leetpvpers, since it changes the dynamics of that greatly. But this shard seems relatively quiet for most of the day (people macroing, etc.) until around 8pm EST anyways, so I thought that maybe no one else saw it. I really can't think of any reason why it might be character-specific.
Re: Magic Reflect no longer requires a cooldown [resolved] I've had this happen to me in the past as well, but haven't been able to replicate it regularly. And agreed - it does seem related to logging out with Magic Reflect on. Just like you describe, when you login you have Magic Reflect on, but it doesn't show in the buff/debuff tray. If you try to recast it, it says you already have it on. And when it becomes exhausted, you can re-apply it immediately.
So the deal here, I believe, is the way Reflect works. Being that Reflect is not binary (either on or off) and can Reflect multiple spells, depending on the level, I think what we're seeing is a lingering little bit of Ref that isn't enough to put up the buff icon, and as such doesn't trigger the cooldown. I've noticed this many times since Beta, where I'll login, see no buff icon, cast reflect and get the system message about not being able to adhere. Hit with a couple small spells and I'm ready to go. So in short, something to do with the buff icon threshold maybe.
I'm not sure I believe that you can have some # of spell levels "remaining" in your reflect shield and *not* see the icon. It seems to me that you see the icon as long as the spell levels remaining is >0 (you guys have way more experience anecdotally than me with this though). It also seems to me that even with the icon and spell levels remaining, you can be hit by a spell. For example, you have 4 levels remaining and you get hit with a flamestrike. It exhausts the reflection and you get hit with it. There are a number of reasons that could cause you to log in with no icon for the reflect buff. That's no big deal - doesn't actually impact any other player, any other monster's ability to hit you, etc. It's just a reporting/diagnostic issue. You try to cast Reflect, it says you can't, so you drop your shield and then recast it. What I'm 10x more concerned with, though, is the fact that for a period of hours thereafter, you can recast reflect immediately once it wears off. That is a significant advantage due to a bug.
