For missions, be they military, trade, or diplomatic, there's one piece of good advice that appears here every so often, "Only send what you can afford to lose."
I'd vote against a higher "defy death" simply because anyone facing overwhelming odds shouldn't have a really good chance of escaping (why not some of the ordinary units too?). You can improve the odds of your commander surviving, simply by posting appropriate levels of force.
Equipping is again a choice: yet another aspect of Illy that has a "soft limit", where you can find an 'unbuffed' limit fairly easily, then work progressively harder for each bonus. Crafted weapons are one such bonus, and use the principle of "work done" translating into further effectiveness in the game. Stack many such bonuses on top of each other, and in quantity, and you'll have a formidable force. Of course, it takes organisation, work, and perhaps cooperation.
As for "war situations" in general, it's difficult to advise, because there are too many variables (another Illy-ism!). You need to be 'ready' before you can successfully prosecute a war.