Abassid heals in combat?!

So let me get this straight…

With the culture wings medical centers, Abassid units can heal while in combat while fighting next to a keep…

Meanwhile, English longbows cannot heal in combat and Abbey of Kings cannot heal units in combat.

Something here seems off to me. Would love to hear someone justify to me why Abbasid should be getting passive heals on their frontline at all times.

You have to age up, research technology and build a keep for healing in combat near the keep, for me is fine.
As English if you want heal in combat make some monks, cost less and you can heal everywhere

Because it takes two age ups, a tech, and a keep for a 2 hp/sec in a tiny radius. Your English longbows get +25/50 % attack speed from outposts in a x2 screen radius. Make monks if you want combat healing that bad.

Resource cost is high to obtain.
Time to invest is also high.
The healing effect is not strong enough to do considerable change. And the radius is short enough that you wouldn’t want to fight under the Keep anyway as you would get hit by Boiling oil.

it functions best as a retreat point for a wounded army, or as a checkpoints along your tradeline to heal traders and keep raiders off.

Keep are rarely an major issue and you would siege one down regardless before pushing forward as fighting under the keeps is akin to suicide and massive waste of resources.