Does magic intensity x2.5 in Master of Magic unbalance the game, eliminating the need for city development and army creation?

I started playing Master of Magic two days ago. For the first scenario I chose Tauron and easy level. Initially the game was a bit hard, but I managed to kill two enemies before it crashed due to emulation issues.

For the second attempt I chose a custom hero: Nine books of sorcery, sorcery mastery and conjurer. Normal difficulty.

Then I captured the first sorcery node by magic spirit: moved it to node, summoned as many phantom warriors as I could, killed some guards, escaped an repeated the process. (I could summon a warrior only for 4 mana, so I restored MP by alchemy.)

This gave me enough of a power base to not have to worry about mana for low-level spells. I captured 5-6 cities and the same amount of power nodes without an army. When I met Tlaloc, my power exceeded his about 10 times.

Does high magic intensity eliminate the need in city development and army creation? (The distant cities can be protected by summoned creatures with word of recall on them.)