I ranked my titan up to 45 vanguard but didn't bother with the other factions much after rank 3 just because I preferred the vanguard. I think its kinda unfair that the other factions get special quests with exotic class and class item rewards but players with very high vanguard and crucible rank don't get a similar quest. I really want those special class items but I'm really not looking forward to grinding 25 ranks!