I don't know why you wouldn't max mages. I have a lvl 92 "fishy" and I find that an extra 5k a second of elemental damage is very helpful. Granted, I do use enigma to keep skellies in line so mages don't block doors and such, but I tend to run open areas more, better for CE and summon army.
I thought about doing bone armor instead of mages, but with 12-15 skellies and 15-19 revives, do you really need a couple hundred point bone armor, or would you rather have 5k more elemental damage, and 12-15 more meat sheilds. While not as strong as reg skellies, they still have more life than you, allows you to retreat when your whole front line dies instantly from IM.
Not to mention for doing things like DClone and Ubers, poison mages give you like 10 minutes of prevent monster regen so you have time to remake your army and come back if needed. Cold mages slow bosses very well, add that to decrep and clay golem and you have max slow.
Based on my experience with this type of necro, (was making them before I knew they were "fishy") in my opinion there is no better way to spend the extra skill points than on mages for the simple reason that everything else on the necro is 1 point wonders.
1 point in revive gets you 15-19 of em, you will find it is hard to keep that many active. Clay golem and golem mastery give you a 9k life golem with just 1 point in each, if he dies recast him, mana is cheap. Curses, if it wears off, recast it. If the mob is huge, cast it twice. Why waste points here for another yard or an extra second.
PnB skills, spear, spirit, nova, etc, in my opinion, are not effective unless fully synergized, so no point in starting these with a "fishy". Anyway, that is my two cents.