First off, why was this change implemented? If it was to stop people from "shopping around for a fresh raid", then you've done that, but you've ALSO caused a real disservice to the people who were already forced to join a previous raid in progress and are now needing the first and/or second boss of the instance to complete their loot rolls for the week.
As it stands now after the patch, we aren't shown the completion status of a raid until we're ported inside and have to figure it out on our own. If we find that we've already downed all the remaining bosses in our previous raid, we're forced to either port out and get a 30 minute deserter debuff, or else kill the bosses again without having ANY benefit for doing so (no loot, no experience).
On my server, when I join a LFR as DPS, the queue ranges between 15-30 minutes, with the average being around 20 minutes, and I'm fine with that. Let's say I queue for the first time and get into a raid after a 20 minute wait, only to find out it's a 1/3 completion, meaning the first boss has been killed. I need to kill all the bosses for possible drops I need anyway, so I don't mind starting with boss #2. I accept the port.
I get through the raid, kill those two bosses, and then requeue again so I can (hopefully) get a raid that's 0/3 and I can complete the first boss. My second raid pops and I port in, only to find it's also a 1/3. Since there's absolutely no benefit to me staying in that raid and spending the next 30-60 minutes killing two bosses I already killed, I would logically port out and requeue. But wait! I can't because I have 30 minute deserter debuff! So now I have to wait 30 minutes before even having the OPPORTUNITY to requeue, then wait another 20 minutes for the instance to pop.
By removing this feature that shows us the completion, you are basically forcing people into a time sink in that they either stick around to kill bosses they've already done (which is pointless) or else punish them with a 30 minute debuff. Either way, you're wasting people's playtime, when many of us have limited time to play as it is. Being an "OMGCASUAL" I have a couple hours in the evening to play, so naturally I'd like to make the best of that time and not spend it being "punished" with debuffs and unnecessary waiting around. I don't expect to get into a raid after 5 minutes, nor do I expect it to always be a 0/3 raid, but neither do I deserve to spend roughly an hour each attempt "gambling" that an appropriate instance pops for me. This can easily result in 2-3 hours to complete an instance that shouldn't take more than an hour.
Had I seen the second raid pop as 1/3, I simply would not have joined it. Not only would this have saved me time by allowing me to requeue, it also would have freed up the spot for someone who maybe hadn't killed ANY bosses yet, or didn't need whatever #1 dropped, and didn't mind joining a raid in progress (like I did the first time).
There are a few options that would make the entire LFR experience fair for everyone:
1) Go back to showing us the completion status so we can decide for ourselves whether or not to join. If we decline, that just opens a spot for another player who may not mind an in-progress raid, and we can requeue without wasting the raid's (and our own) time.
2) Don't show us the completion status, but don't give us the deserter debuff if we leave after seeing that we've already completed the remaining bosses. Let us leave and requeue, then give the spot to the next person in the queue.
3) Give people a checkbox that allows them to queue for ONLY fresh instances and/or for instances in progress. This way when an instance pops, you'll know it's one that you can actually benefit from, depending on what you've already done for the week. This does NOT mean that people will only queue for fresh instances all the time, because I think many people don't mind what ORDER they kill the bosses in, as long as they only have to kill each one once.
TL;DR version - please reconsider showing the number of bosses downed, or else eliminate the deserter debuff.