I tried a slightly more magic heavy set up some nights ago. I normally just use a SS with Darkstar Cloak and a lv2 with tome of furion and it suffices. (I take Dark magic lv4 and Shadow lv2)
It works fine like that, it can be really hard to get those shadow spells off with only a +2 modifier, since from spell #3 onwards, it jumps from 10+ to 13+ to cast, but it's ok for me since Shadow is just for support, its spells aren't mandatory (unless we need mindrazor for forty spearmen fighting a WoC deathstar unit then that's a different story- eight dice IF go go!). I've swapped lv4 to shadow a few times, i found it worked out worse, which i wasn't surprised. A lv4 using Dark Magic consumes fewer dice, saving that extra one or two to fund shadow spells from my lv2.
The other night I added in a lv1 mage into the mix. I intended to swap out Darkstar Cloak for a Dagger for my lv4 (forgot about the equipment switch
), who went shadow. My lv2 kept her same kit and took fire (wanted to try it out) and my lv1 took dark magic for chillwind spell. Only one measly extra spell into the mix, I scored six PD on average in my game against WE, and consistently channeled an extra die.
During the turns where not all my spells were required, it was ok. When it came to requiring all my debuffs from shadow against his dragon munching my spears, then chillwind and miasma to fire control his fifty glade guards, then sword of rhuine to chop his treeman up etc etc, it required a lot of risk to gather just enough PD, which I only partially succeeded with.
The issue is that if you fail to cast, that's it for that sorceress for that magic phase. And when you really need your spells to go off, you don't want to just throw one die at PoD on your first cast for your lv4, and you want to make sure you cast a spell off at a value that's hard to dispel, so you add an extra die in etc etc.
I imagine it would've been a whole different story if I had used the Dagger, it would've allowed me to use the minimum PD from the pool and bumped them up if necessary, giving more dice for my lv2 and 1 to use. So I reckon it's feasible going lv4 and two lv2s, but you'll really need that sacrificial dagger. I'm going to try double lv4 next, and I definitely will be taking Dagger for the shadow mage.
And that's the other thing to consider too, as masamune had said, it depends on what lores you're taking and what spells from them you want/need, that's your major determining factor for how much PD you'll be consuming and the appropriate equipment to help solve that financial crisis. Note you probably won't be using half of your spells each phase anyway, you might be using fireball and chillwind at turn 1 and 2, sniping the BSB at turn 3 with death spells, then the withering and mindrazor in turn 4 and 5 when you're in CC.
That's my feedback from what I've experienced so far for 8th ed. But definitely don't go <3 mages or else you'll have jack all hitting power and too many spells unfunded!