Dalaran would inevitably have to leave. In the future war against the Lich King, the city would become a staging point for both the Horde and the Alliance. Of course, that was how things had gone in the original timeline. Rex's presence had changed a great deal in this life, but in his eyes, Dalaran still had to leave. Even if it had no intention of doing so, he would find a reason to push it out. Having Dalaran within the Kingdom of Gilneas was uncomfortable for Dalaran, but truth be told, it was uncomfortable for Gilneas as well.
A state within a state brought all sorts of problems that needed solving. It would be better to let Dalaran leave. Rex believed that, given the opportunity, Dalaran would certainly do so.
If Dalaran stayed, it would remain a state within a state, subject to heavy restrictions from the Kingdom of Gilneas. Once it left, however, it would no longer have to worry about Gilneas.
Rather than live in constant anxiety, it was better to gain freedom.
That was Rex's understanding, and Dalaran's leaders thought the same way.
Launching a campaign against the Lich King would be no easy task. In Rex's opinion, dealing with him would be even more troublesome than facing the Burning Legion's invasion under Archimonde.
If the two were compared purely in terms of strength, then naturally, Archimonde's army of Burning Legion demons was stronger, while the Lich King's undead army was weaker.
But when Archimonde led the Burning Legion's invasion, they were outsiders storming into foreign territory. They paid no attention to strategy and simply attacked, charging recklessly through everything in their path. In the end, Archimonde's underestimation of his enemies proved his undoing, and a massive explosion finished him off. Without him, the Burning Legion