The magic resistance thing is really needed for summons. It probably shouldn't be too much, but i feel a little is necessary. Something along the lines of YOUR summoned minions gaining a little magic resistance each time you level the summon skill (maybe 5% resistance to magic each level?(idols come with preset resistances?)) and the morale skill should give like 1,5% magic resistance each level. Meaning for something like 30% magic resistant minions in the end if you go full general.
Although more minion resistances might be nice. If they could get a speed boost some how, they'd be much much stronger. But otherwise a good general build is just as strong if not stronger than good assassins
Speed is a major issue. I just don't worry so much about enemy minions they take forever to get to the fight, and I can always outrun them.
I don't think speed is an issue, since (i don't know maybe it only seems this way to me) if you select your minions and demigod at the same time (hotkey N, if i'm not mistaken), the minions move at the same speed your demigod does. For example: i was in a game with Sedna, and decided to play around a bit when we were winning just for the heck of it. I had boots of speed, journyman treads, speed wand, swift anklet, wand of speed, cloak of elfinkind for my movespeed items (i know, lots of speed heheh) +the skill that grants her movespeed and HP regen maxed. Also i decided to take yetis and lowest level idols just for fun in the end. I summoned my yetis and minions at my base and selected everything together and sent them to the enemy base. And what do you know? Everything was on the same movespeed. If you add up the bonuses then you'd see a total passive movespeed of 10.5 and exactly 15 if journyman triggers and if you use wand of speed too. Maybe i really was seeing things, but its happened to me more than once. So if what i say is true, then no, minions need no speed buff. But if it turns out to be false, then yes, minions desperately need it.
PS: The only way (i think) to get even more movespeed would be if you were UB (base movespeed 6.3) and had Oaks surge of faith buff and TB fire aura and if you had all-fathers ring included on the list of previously named items. Maybe i haven't found it yet, but there seems to be no other way to get higher movespeed. With all that i think your total movespeed should be 100+85% passively or 100+195% with buffs and stuffs (movespeed 18,585).
PPS: Actually when i think about it Oak could theoretically get 100+235% movespeed with last stand, but you'd need to luck out with journyman and you'd need to activate speed wand and surge of faith and die at almost the same time (movespeed 20.1)