I have some hints what u could make better:
Decrease Armor of every unit!!!
Having 90+% dmg reduction is really annoying.
Make more skills and skill lvls
GIve all charakters custom skinns

How about a trigger if u have like 3shikon shards in ur inventory they turn into a biggger shikon shard and so on so that u are able to collect 1whole shikon jevel?And how about giving the corrupted shikon shards a ability that slowly drains health from u and u have to go to a special place or kill a specific monster too "free u from the curse" and make them normal shikon shards.Oh and how about changing the shikon shard bonus from +5
+50
+5
to
+50
+5
+50
Cause u get a incredible armor boost by having 6shikon shards with koga for example.
This is only my opinion so please dont blame me for it