Every time 'hard' content was made outside of heroic raids (heroic 5 men in BC, heroics in cataclysm, first tier of normal raiding in cata was a big step up even without counting heroic raiding etc) there is so much bitching and backlash from most of the players that shit gets nerfed fast and hard. The difficulty progression as it is right now is fine. LFR to flex to normal to heroic is fine.
If you're a heroic raiding guild you won't spend long doing any of the other tiers.
If it takes you forever to clear normal and you feel you don't want to progress in heroic, it means normal was tuned 'hard' for your guild and you probably would break your face on heroics until the next tiers come out.
Everyone can see the content now, and do so at various levels of difficulty, what the fuck is there to bitch at?
And spare me the 'but but but I'd rather have 1 easy raid 1 medium raid and 1 hard as fuck raid so the content is not always the same during the difficulty curve'. If they did that it would be a fucking revolt because only the 'elitist no life raiders' could see all the content.