Splitting the functionality of RoH up presents a *lot* of problems. WAR gets away with separating the functionality of its combos because it's been designed as such. The "utility" combos both generate laughable enmity compared to the high enmity combo but make up for it by increasing the enmity that the high enmity combo generates (by increasing their damage). If Maim did something *other* than increase damage, you'd see much the same issue with WAR as you currently see on PLD. The Maim combos justify the loss of direct enmity to end up being a net increase to enmity generated indirectly.

Any reduction in the effectiveness of the PLD rotation has to be made up for elsewhere. If you want to require PLDs to use a low enmity combo every 2 combos, you have to increase the total enmity of the high enmity combo by ~20-25% to make up for the imposed loss. The problem with this is that, if you increase the enmity of RoH by 30%, you're just making the RoH combo more attractive. Unless you simply copy the Maim model that WAR uses, you would have to make the benefit of the low enmity combo so huge that no PLD would ever want to go without it. At that point, you end up just making PLD stronger, which upsets the balance structure (since a 10% reduction in STR isn't really a massive boon).

PLD just isn't built to use more than one combo for tanking. About the only thing that you *could* do, without simply copying WAR, is to make it so that PLD actually has a legitimate reason to use Shield Swipe while tanking by giving it a high enmity modifier. At the very least, it would change up the PLD rotation by adding in an element of randomness.