Yep, sure is. There's no channeling limitation in combat either, for whatever reason.
It'd be a totally separate post, but I personally really dislike mana as a balancing method, because it's binary: you have it or you don't, and if you do, you have infinite spellcasting. I'd rather see a cooldown based system, possibly with mana used to infuse magic item creation or certain specific very powerful ritual spells with game changing effects (a 'currency of power' vs its current implementation).
That's a radical change however, so I've been hesitant to make a post about it, given how many other aspects of the game need polishing right now.
I think adding an expensive mid-late game tech that allows for expensive, slow transit between cities (one unit/turn or less) would help for late game travel, and adding on-map portals with restrictions (guardians, in-transit guardians, fees to use, etc) to medium and large maps would also be a boon for the AI, and give another interesting strategic wrinkle to deal with.
Otherwise, on medium and large maps, fighting effectively vs enemies on the other side of the map is difficult or impractical, barring abusive tactics (hero stacks instantly razing cities, etc).