I agree, something needs to be done to make it more powerful. I frequently see many Rohirrim die while under the effect, even though they are taking only 10% normal damage. I have 3 suggestions: Change the Rohirrim's trample effect to continually cause trample damage even to units that have been knocked down on the ground(Like the Mumakil in BFME2 1.06), so that as the entire army passes over the enemy units they keep damaging them. That would better simulate the effect of a massive cavalry charge, it doesn't make much sense that because enemies are knocked down they don't take damage. Next, make this ability ignore enemy abilities that make them immune to knockback, like the Veterans for example, as those abilities basically neuter this one. Finally while under the effect of Glorious Charge Rohirrim should be immune to Crush Revenge damage from pikes.
I didn't know the Tent Rohirrim had less health, that's interesting. But they do grant additional armor and damage, and can switch to bows, so honestly I think that's a fair tradeoff. What they REALLY need is to get Fire Arrows along with their Forged Blades, and arrows that pierce heavy armor. Then, like the trainable Rohirrim Archers, they would be an effective counter to heavy pike spam, without being so weak in health and armor, increasing the value and versatility of the tents over Ents.