There're far better combos for when your cultural retinue sucks than spamming HI. Defensive and Skirmish for instance.
Defensive on its own is a pretty good retinue for stacking. It's not got a particularly high cost, the archers slaughter your opponents in the skirmish phase and the pikes prevent you suffering major damage in the melee (with the right-cultured generals, they can deal absolutely horrifying damage as well, and they even give fairly good damage with generic tactics). Then it's also good at siege-assaulting due to being composed of 40% Archers.
Likewise it's good when combined with Cataphracts (although some might just prefer pure Cataphracts). If you have your Defence retinue in one flank and your Cataphracts in another, then the Defense retinue lies about its name by brutally smashing your enemies to pulp in both the Skirmish and Melee phases, while the Cataphracts (who will likewise have performed decently in the Skirmish phase and very well in the Melee) then merrily slaughter the shattered weeping routing elements of your enemies in the Pursuit phase. The presence of 20% Archers in your army also means that siege-assaulting isn't much bother.