Aye, I did have some time to prepare, and I tried to make most of it. I started building high-MR SC's from the moment I witnessed Pythium master enslaving Van's army early in the game. At that point I knew putting conventional armies in the field was most likely to just gift my opponent with free troops.
Of course, after the defeat of Pythium you were strongest nation left, with quite a bit of astral magic of your own, so I just continued down the same road.
I agree that Arga Dis is a strong nation, for the reasons you mentioned and a few others (if we're talking in the context of late game they also have the ability to develop a really good magical diversity from their national mages and summons, without pretender help for example) Do you have the impression that they are too strong, as a nation? I myself don't, they have a number of weaknesses to balance their strengths, but I'm happy to hear other opinions. I'm sure Sombre would also like any feedback you might have on the nation. (though to quote from the guide I wrote on the Arga Dis nation: "In my game I managed to recruit about 40 mages without getting a single 2E one, meaning no site searching, and, maybe worse, no earth boots -> dwarven hammers. I ended up having to empower one mage to 2E. " so getting to hammers wasn't exactly easy for me this time around.
)
I have to say I also have had outrageous luck with my magic sites. Loremasters help, but to be honest they're the least of it. I won't give away everything while we're still playing, (I can tell you the specifics when we're done) but let's just say (the) god(s) is/are entitled to at least a votive candle or two.
Oh, and I love ghost raiders. Must be my favorite spell in the game. I got reamed by Calmon using them in my first ever MP game, and never forgot.
I've set the timer to 72h. I just started working again today after being in-between jobs for the last couple of weeks, so I'm not entirely opposed to the idea myself either.