Perhaps for 10 man, you're likely to shard it. Say Joe and Bob are both rogues, and there's no other agi leathers in the group. Any further agi leather gear would be dissed anyhow. But what about 25 mans, where the other rogue is then getting all the agi leather gear, or perhaps the monk or feral druid is? Or what if you also had a Brewmaster in your 10 man group, who's suddenly getting all the loot, rather than having to share it with Joe?
As said, it would start to become really advantageous to send one half of the raid squad to LFR before the raid, so they get the LFR gear, and you're still able to give all the gear to the other half of the raid, so you're not really wasting any. The next week, you switch it around, and send the other half into LFR first.
These aren't things that change from current. If you wanted to give loot to half the raid, you already can. And the other half is already doing LFR, so at worst case you're .... not changing anything for 100% of the people
And... What's Bob going to get from all this? Perhaps it's his first time in normal, and he's getting a decent experience while helping out his friends. But what if you can't take Bob but have to look for a random. That random ain't going to get anything at all from your run, so he has zero incentive to tag along.
That thing you just had in the second sentence. It's an incentive.
You still come down to the choice "Do I want to go ahead and run LFR this week, or should I try and remain unlocked, in the hopes that I can join a normal run and get some gear there?" Blizzard clearly stated they do not want to force players to make that choice.
Early on in the new tier, yes, it's quite likely to get two pieces per week, since you can still use about everything.
As for upgrading a 553 ring or a 540 chest... I'll probably going to keep that ring for a while, while the 540 chest will be replaced pretty soon, even if I upgrade it, so I'd likely upgrade the 553 ring, especially if I have a 543 chest as well, making the chest upgrade only 5 ilvls, rather than 8.
How do you plot that? The likelihood of you holding onto that ring is the exact same, since Rings are more generally dispersed, you'll have access to Heroic Rings from week 1 of Heroics. Moreoever, unlike with the Chest, you're just as likely to haev the exact same ring drop as you would a different one.
And if you've been getting 2 pieces a week on average, and everyone in your raid has been in the same boat, that's some pretty ballsy luck going on there. Bearing in mind that you WON'T use just about everything. Even for us as Paladins, a 553 Dodge/Parry piece is not going to be as attractive as some of the 543's we're using now. Some of the offset pieces won't even be worth using for specs until they have all 4 pieces, or will never be used over tier pieces. Cloaks are pretty guaranteed to be sharded in any normal raiding guild.
You still come down to the choice "Do I want to go ahead and run LFR this week, or should I try and remain unlocked, in the hopes that I can join a normal run and get some gear there?" Blizzard clearly stated they do not want to force players to make that choice.
This isn't a choice, especially since LFR is winged and a person is not going to just pop into a Normal run and kill Garrosh at the start of the tier. A person who openraids Flex has a pretty much guaranteed kill, on the other hand, so there's no choice to make for him/her either.
But it will make the other half get more gear... Sure, there's intellect plate, but there are also a ton of items that have a lot of overlap between different people. Several people being on lockout would certainly mean that there are a couple of pieces going to other people on default, that might've gone to one of the other people that are now on lockout, especially in 25 man.
But that's something that you can already do. If youw ant your BM to get the loots, you can give him the loots regardless of if the Rogue is locked out or not. On Live, the Rogue is also supplementing with LFR in said hypothetical, so his continuation of LFR for his loot is no change on his personal part, so you've got 50% effect, which doesn't really destroy the entire premise.
Besides the fact that this would complicate the UI, and lead to a lot of issues and tickets about "I forgot to enable/disable loot eligibility", it would also force people to make a choice "Should I run LFR this week and get some loot from that? Or should I remain unsaved in the hopes that I run into a nice group?" Blizzard already stated they don't want players to have to make that choice.
See above regarding choice, and I forgot to enable/disable DOES actually fall into player responsiblity.
More to the point, it doesn't complicate UI any more than selecting your Role in the Dungeon Finder does.