I recently played a game with the mongols at deity and win it easilly just by only rolling over every empires with about 12 keshik and 2 horsemen (at the end these horsemens were upgrade to cavalry and to tank, but they were basically just there to took the city after my keshik did the job) . My keshik unit were usefull on the battlefield until the end of the game, that ended in a domination (I was just about to replace them by massive aircraft army)
I've been able to done that for two reason:
First: Ten of my keshik units had the 2 attack per turn, +1 range and the indirect fire attack, witch mean i can attack 20 times at every turn and retreat far away from the line since the keshik has a 5 movement point.
Second: Because of the combat system that make sure that I do at least 1 heal dammage to wathever my keshik attack (even the GDR).
What would happens with the new healing system? I dont know, but i really expect that thereafter, my keshik would continue to make 1 heal dommage to a GDR, but since that GDR would now have 100 healpoints, i wont be able to kill it with keshik until I have 50 of them with the promotion already cited.
I also expect that if that GDR attack one of my keshik, it'll kill me in one shot while my unit does a 1 heal dammage, witch must still be the basic of all combat. You never notice how bad it's when your GDR have to heal himself every 6 to 8 turns because he is walking on archer, swordmen and pikemen? Because there is a 1 basic dammage everytime you engage combat, it mean you lost 10% for every combat, but with 1 dammage out of 100, you lost... well its math.
Even the bomber get a 1 point dammage against archer and crossbowmen (dude how the hell can a archer do 10% of dammage to a bomber, even 1% its to much, but lets says that the bow just crap the paintwork on the side of the bomber.
In fact, I really think that the change in heal point system will improve the reality of the unchallenging combat between two units that are not of the same era. You'll also be able to profit of your technologic advance on the battlefield, since you wont need to heal your units every 4 to 6 turns while clearing field.