I'd say that any state that makes humiliating demands on the religious practices of a foreign country, then waging total warfare on said polity when they fail - inevitably - to comply, is absolutely totalitarian. Also, the fact that there were political exiles at all strongly suggests, I dare say even necessarily demands, a totalitarian regime that abides absolutely no deviance from the acceptable forms of towing of the party line. Green-Fire Night was just the icing on the murdercake.
Then clearly you didn't pay enough attention in history class. That simply isn't what totalitarianism means. The Crusaders who wanted to make Jerusalem and the Holy Lands Christian were Feudalists, not Totalitarian, and nearly all forms of government have frequently engaged in opposition/dissident-slaughtering. Kings, Emperors, High Councils, Khans, Tribal Elders, et cetera, will and have decided that some form of opposition to their rule could only be answered with exile or death. When peasants got uppity, they often got the sword. When someone spoke out against an Oligarchial council, they usually weren't just answered with words. Most things aren't WWII, and most forms of harsh, brutal government aren't totalitarian.
To be totalitarian, a government must believe that it is the ultimate authority on all things, has the right to pass any sort of law it wishes, and must actively try to use all of these powers, regulating as many things as it can, in any way it wishes. This appears to be incompatible with what we have seen of the Dominion, since they appear to hold tradition and religion to be superior to their own authority. Il Duce, for example, regularly disregarded the Pope, whereas it seems impossible to imagine Alinor going against the wishes of Auri-El, given their great religious fervor.
Also, totalitarianism was crazy in ways that the Thalmor aren't*. Here's a quote from Il Duce: "We must finish once and for all with the neutrality of chess. We must condemn once and for all the formula 'chess for the sake of chess', like the formula 'art for art's sake'. We must organize shockbrigades of chess-players, and begin immediate realization of a Five-Year Plan for chess." In a totalitarian state, literally everything is (supposed to be) about the state. Totalitarianism is a very unique form of extremist governmental dikeishness, not a blanket term for every sort of dikeish, brutal government.
In summation, totalitarian =/= murder-happy dikes
*not that the Thalmor aren't crazy. They're blinded by hatred and refuse to pursue their goals in anything resembling a logical plan.
Also, seriously, dike isn't censored, but a synonym starting with "p" that also refers to the things porcupines are covered in is censored. Is that word waaaaay more offensive in some other country, or what?