Just finished a game on Normal difficulty and encountered some AI issues:
(1). The AI was extremely passive with its fleets. It made no attempt to either intercept my invasion fleets or invade my planets, instead dividing its ships among its planets where my combined fleets could crush them individually. I felt I was fighting a collection of independent planets rather than other civilizations.
(2). The AI did not attempt to invade my planets. I left most of my planets undefended in order to focus on offense. I thought this strategy risky and expected to lose a couple planets, however despite being at war for most of the game enemy fleets never came near any of my planets.
(3). The AI did not make any alliances to counter my expansion. My opponents seemed content to let me gobble them up one by one. If I've conquered half the galaxy, I should be fighting a coalition of most of the other races. It's both logical self-preservation for the AI and keeps the late game interesting.
Anyone else notice these?