ancient uber mage...hmm, now if only morrowind had some of those.
oh wait, they do. what are they called again?
right...Telvanni.
your argument would be legitimate if you took into account the power of the Telvanni House. This isn't some local hole in the wall Mages Guild defying an empire. Its a couple of thousand(s) year old mages who have pretty much seen more than most mortals have. Remember, the Telvanni were the ones who closed some gates in Morrowind during the crisis. While it is true they did not act in previous engagements, I think the Telvanni have the power to summon large numbers of troops to aid their house brethren. If only the houses could stop tearin each other apart and unify under a warleader...like a Hortator or something.
Indeed, they might have closed
some Oblivion Gates. Or rather, to be exact, the quote goes "I have heard things are bad in Vvardenfell. The Telvanni do their best to close the gates, but it is to no avail". The Gate closing business wasn't going very well for the.
In addition, the ones that they tried to close were probably just those who threatened their territory, because they do not give a damn about other people. Not even their own lower classes, probably. They would not take part in a war against anything (Non-House) unless forced to, not untill (in this case) the Empire came to close to their own islands. And even then, som of them would probably ally with the Empire just to be able to conquer their neighbours.
as for the whole "arrow to throat" argument....All you need is someone to cast a wide effect shield spell. And just because the game doesn't allow you to do it doesnt mean the Telvanni are incapable.
Or a wall of fire, burning the arrows to ash. Or a large telekinesis wave, disrupting the arrows' flight. Even large, otherwise very deadly arrow rains can be dealt with this way. I think, the best way to deal with large quantities of mages is to engage them into close combat.
Though getting close might prove quite difficult, not to say very dangerous.
[font=Georgia]Well, not everyone in House Telvanni are thousand year old super mages, in fact, their leaders may be, but we all know the Telvanni have a selfish love for themselfs, and I doubt you will see any of their masters exposed on a battlefield. Even if, Magicka is still limited, and does run out. Unless they had a huge supply of restore magicka potions or something they constantly drank, then there great armies of creatures would fall apart.
A wise mage-general would of course only apply a part of the mages under his command in battle at one time, letting the others rest and restore their magicka. If it was me, I would use at least three or four different shifts, to make sure there is and almost rested reserve to use as well.