I understand what GW was trying to do in 8th ediiton with winds of magic by making it such that you could go without any mages and still have some decent magic defense (you get the greater D6 of the 2D6 power dice in dispel dice)) and some hope that the opposing general will not roll welll in terms of winds of magic. Also, you can run a single mage in 8th edition and, with a good winds of magic roll, get off a lot of magic. I also understand that GW designers (esp. Matt Ward), think some randomness is "fun" or "interesting" for the game and, to a point, they are probably right, especially for newer players. As the new army books have come out written for 8th edition, they have taken away or reduced the ability of armies to generate a lot of power dice in addition to the winds of magic without a significant points commitment or risk., except with the lore of death. Notice that they also have gone away from the uber spells that both do not allow for any save and either hit and destoy all models in the unit that fail some test or hits and destroys all models touched by the template and fail some test (or destroys the number of models rolled for in the case of dreaded 13th) in the newer army books as compared with the 8th edition common book like purple sun (lore of death vortex spell), dwellers below (lore of life direct damage spell), and pit of shades (lore of shadow direct damage spell).
In 7th edition, the number of power and dispel dice was determinable based on the mix of mages taken but the rules could be abused such that one ended up with mismatches occasionally against some armies in the magic phase (like against some Liardmen, Daemons, dark elf sac dagger and power of darkness , and vampire counts builds). The spells were also generally less powerful but miscasts were less damaging. The ability to take multiple dispel scrolls also helped a bit.
The biggest problems/complaints with 8th edition magic are the lack of scalability for smaller battles and the dislike by more experienced and tournament players of the randomness of the magic phases combines with the semi-autowin spells in certain match-ups making the game less predictable and too often based on luck. We often house rule the scalability issue by having the winds of magic reduced to say 2D3 power dice and the greater D3 dispell dice at or below 1000 point battles and scale up from there to 2D6 at only 2400 to 3000 point battles. [ 2(D3+1) dice for say 1250 to under 2000 point battles for example]. Otherwise, in smaller campaign and warband events and escalation events, armies with cheaper mages can cast a lot of spells and armies with expensive mages can't cast at all given the character points limits (or are at a disadvantage). When playing larger team battles, we have a modified power dice pool and dispel dice pool scaled up to the size of the armies and number of players on each side.
