My legendary balance warlord carries 2 manders and 1 spectral minion because sometimes a minion can turn the tide of a game, or at the very least, be a mosquito buzzing your opponent's mind.
My main goal when I cast a minion is to get my pips worth out of them. If I get 3 useful spells from my minion, I figure I got my pips worth. Sometimes I get 10-15 spells from a minion before he is killed, and I definitely get my pips worth then. Unless, of course, my spectral becomes a water elemental which is the worst minion in the spiral, but maybe is a touch better than nothing at all.
Obviously, carrying so few minions, I can go a whole game without one, and can still win without them. They are a luxury in a way, but still a valuable tool in certain situations.
Occasionally a minion is killed right away, and that is sometimes OK because it made my opponent use a spell against my minion and not me. Unless they had a group spell like fire dragon or myth frog. But maybe my opponent would have used efreet on me instead of dragon, so again I think it works out for me, in that I suffered a lesser spell because of my minion.
Also, casting a minion can really annoy your opponent. Don't be surprised if you get called a minion noob. My feeling is anything that annoys my opponent is a good thing.
I usually will NOT cast a minion against a death wizard because they can easily gain 500-1000 health from my minion with scarecrow, so casting a minion actually hurts me instead of helping.
The problem with casting minions is they take a couple valuable power pips early in the game, thus giving your opponent an advantage in the pip war. Having a minion is useless if your opponent turns that pip advantage into a win.
Sometimes your minion is killed right away and was a waste of pips. So be it. It happens.
As far as death wizards go, I almost never see them casting a minion. They must not cast many useful spells. Or they are simply going for the multiple bladed dragon of death that I dread more than almost anything in the arena.
I have a fire warlord who isn't legendary, but is level 49. He uses maximum minions because the fire minion has a few very useful spells. I don't know if I'll use as many minions at legendary, but I anticipate I will.
He casts Black Mantle, which is a great spell. But the real benefit is the fire elf and link he casts so often. This is a fantastic shield breaker. In fact, my heckhound, followed by my minion's fire elf, makes the heckhound unblockable. I'm not even sure triage would get the hound off in that situation (Haven't seen anyone try triage with multiple DOT spells on them).
I think a reason many people use minions is because you are usually ahead in wizard city and early krokatopia but once you hit the krokosphinx you start to get behind the average wizard. This has a effect on most which makes them want to win more easily with minions. In mooshu you see many wizards with dragonspyre armor and minions. My point is most people are used to using minions and they associate your health and power to celestian bosses and they try to get to help from any source possible.
Finnigan Fireflame