Yeah, no. Blizzard hasn't banned those top-end guilds for multiple "exploits" over the years, possibly because a lot of them could be passed off as clever use of mechanics which Blizzard then went in and said "no, that makes it far too easy."

The rules for the LFR tool and loot were stated very prominently in FAQs and answers to questions about it, and even in-game, after killing a boss there is a "caution" symbol that will tell you which bosses you have already looted - implying, of course, that you cannot loot them again. Further, getting pieces of loot off a raid boss multiple times per week seems intuitively against the nature of a "raid," although that may not be obvious to people who are just getting their feet wet with the raid finder. Regardless, it was actually somewhat difficult to use this bug - all of the 25 people queuing had to be there before you queued. An extremely casual player who didn't really raid before the LFR would likely not have access to 25 individuals geared enough and in the proper roles to do it. You definitely had to do this on purpose.

In other words, I wouldn't worry. If it's something that can be exploited accidentally, or is not obviously against the rules, Blizzard has not (in the past) come down very hard on people. The LFR rules were clearly stated from the get-go, and the exploit was very definitely against those rules, and also difficult to do by accident, so Blizzard dropped the ban hammer. Whether they deserve it or not can be debated to death, but the fact is this was a different kind of exploitation than past ones, and so the punishment was therefore different as well.