There are bosses even in 5man heroics where I have infinite rage even whith Inner Rage and HS spam. (For example the boss on the ship in deathmines when I have a near 20 debuff stack, but there are others, too, especially when they have those 30% enrages.) I don't use Inner Rage much, but there are situations where it's nice too have because you really get more rage than you can spam in any case at least at current gear level. Well, one has to monitor the rage bar, and be ready to cancle aura it when the situation changes but it's fun as long as it lasts.
HS spam may be best tps/dps wise. But there are things that are more important than this increas in some situations. HS needs a high amount of rage and there are those encounters where one just need a set amount of rage for special things (spell reflect, interrupt, stun, debuffs,...). In such situations it's better to stop spamming HS and maybe going back to the normal rotation while monitoring the rage bar. So use it when appropriate, but stop using it when it may let you unable to do more important things than pure dmg/threat.