In my nexus days I recall magic was usually at the regular level, and occasionally the norm would be at +1 level, but it was most heavily influenced by the who list. Not items or deaths of ragers/mages.

When villagers logged in, it dropped down. A Commander and a drillmaster and it was almost impossible to keep the veil at average. And it really took a fair amount of mages to have any noticeable impact on keeping the non-shifted level above normal. Maybe a lich would, but the average mage had minimal impacts.

The only time I would say you ever bother with items for the veil to boost magic is pre-raid. Otherwise, you're wasting time cause the effects never seemed to go beyond a day or so. But I would always drop like 6 items, then go raid battle. I'd say the same for Battle, but for them it is harder to stockpile magical items for tahren so it was a less viable tactic for defenses. But if you're raiding a mage heavy defense, go grab a few things to feed tahren first.

Any time you see the echo for a shift in the veil, I feel like those impacts are a day, maybe two at most.

So the veil is really shaped by who is online more than what you do. Which is probably how it should be, although I'd say it disproportionately weights villagers to mages, but I suppose when first implemented mages were more plentiful than ragers.