Remove LFR and make flex slightly easier. This would:
1) Allow even the bad "casuals" to get through it if they bother to find a group
2) Build server communities and get people interracting with each others again
Also make more challenging 5mans with slightly better rewards to make the progression curve smoother, kinda like the troll dungeons in 4.1 (during t11)
So ding max level > dungeons > HC dungeons > 'elite' dungeons > flex raid > normal > HC