It's more like, 10mans will get 1 Legendary, 25's will get between 2 and 3. The old numbers that let heroic 25s already complete 1-2 staves was a major problem to Blizzard and so they nerfed it for the future. That's a bummer to everyone who didn't get to wallow in the good-times, and a blunder on Blizzard's end to not have noticed sooner. It's not however some sinister plot against all that's holy. If you want to complain about comparative staff completion, consider the rates going forward, as that's pretty clearly where they aimed their sights conceding that they really couldn't do anything about drops already received.
The change is sensible, far later than such a change should have occurred and there are some consequences to that delay. It does not represent a vindictive attack on 10's no matter how victimized you may feel.
I don't think anyone is seriously saying its a specific attack on 10s intentionally but the end result is that's exactly how it works out. A 25 man guild starting their first legendary today would get 2-3 staffs but the fact is that FL has been out for a couple months and most 25 man raiding guilds have already completed 1 staff at the very least. High end guilds are about to complete their 3rd (or have already done so) and many 25 mans have 2 already. So you will have most 25 man raiding guilds ending up with at least 4-5 while 10 mans will only get 1. That's a far cry from the ratio Blizzard said they wanted.
I'm angry at Blizzard for a few reasons regarding this change. First - I'm amazed that they could not somehow foresee the rates at which 25 man guilds would obtain the staffs. There's a bit of RNG to the gathering portions but its not a huge difference and if you looked at the average numbers of each item that would be obtained you can clearly see how we got here. Someone had to make the decision as to how many of each item would drop for each type (10/25/normal/heroic). And then likely that had to be approved or vetted by at least a few other people. So how does that simple math escape notice?
Once you get past the initial development phase and onto live realms it was again too long before we reached this point. Obviously data is gathered from all aspects of the game so its a lot to sort through but I would have to think that something pertaining to a legendary would be tracked fairly closely. So either that data wasn't monitored well, which is a big problem, or it was and their reaction was way too slow. Either way it is an issue.
Finally, there is no reason that this change had to be implemented all at once. If this was their end goal as to the drop rates (and this change does ensure a pretty good ratio between 10 and 25 going forward) then they could have implemented it in 25 man at this time while waiting a set amount of time to allow the leading 10 mans to have the same relative drop rate as the leading 25 mans experienced, and then made this change in about 6 weeks as 10 mans would be completing their first staff. This would allow 10 mans to get about 2 staffs, depending on progression, as 25 mans would get 5, again depending on their progression and acquisition rate. That keeps things to the ratio they promised and ensures that 10 mans wouldn't have to wait until this tier is completely trivialized to actually obtain their first staff.