I remember that some topics sparked a lot of conversation back in the days of Dominions II, and I wonder if any of the suggestions have been incorporated?
This spell has a long history of being in the center of attention for reason or another, including being bugged for long. IIRC many felt this is the sole reason why some nations (Marginon, TC) are 'held down' so to say
Many felt that they are not worth their cost, and many suggestions were made to improve them. I remember suggestions to add some sort of skirmishing battle order.
Tien Chi & Barbarian Kings
These, especially the latter, were felt to be lacking by quite many from what I remember. Summonings that didn't match their paths, cavalry that couldn't be fully utilized because there wasn't "fire and attack" option and mages with low astral were felt to be the reasons.
Suggestions to add Chariot troops for Spring and Autumn were made.
Barbarian Kings was felt to be a weak theme by many. One of the most interesting suggestions for them was adding a "Attakc and Pillage" command giving them, or at least some of their commanders, the ability to pillage for free troops.
I believe you've already done something to it.
Same as Life Drain
So...what else? I can't remember everything myself.