... for randoms unless Blizzard makes these changes. And even then, I'm not sure.
First, please have a good look at the official feedback thread on the forums. ... And then please remember that this is the PTR. The players there are not typical players. Almost every PTR player is much more invested in the game than the average player on live servers.
Blizzard's approach so far has been to tune the difficulty down. And that is necessary. But it is not enough. The current implementation would only work if the difficulty were so low that half the raid could kill the boss - without a tank. And if Blizzard, indeed, dumbed it down to that level, the raids were just timesinks to get better equipment. Boring activities done by players for external rewards.
If Blizzard wants this to work they need sophisticated social engineering and incentives. Here are my suggestions:
First, any LFR group starts with a 5-man group. This 5-man group pays 2000 gold to start the raid. This group gets 500 gold back per boss the raid kills successfully. Only this 5 man group can kick another player in this raid and only if they all agree. They cannot kick each other. If one of them leaves, he is replaced by a random. If the groups kicks more than 20 players, the raid is automatically dissolved.
Second, every random player who joins the 5-man group's raid pays 200 gold to join. He will only get these 200 gold back if he is not kicked from the raid.
Pretty draconic, yes? But nothing less will suffice. Read the PTR feedback post!