If the AI has revolted to slavery, I'd expect him to whip an archer as our axe(s) approaches. Has either revolted yet?
If we switch to an axe as soon as copper is mined, We can have an axe on Turn 38. I agree that if we rushed with 2 axes and found two archers in the AI capital, we would have to refrain from attacking and wasting two axes. If we found an archer and a warrior ... that might be worth attacking with one and checking the odds for the second one if the first one dies.
I think the odds would be at least 60% of winning -- 20% on the first turn and over 50% on second with slightly wounded axe vs. wounded but promoted archer. Even so, I don't like the risk reward.
This would seem to be an argument in favor of sending out a single axe as soon as possible. If he finds an archer, he just sits tight and will be really tough to get rid of. The AI will just sulk. If he finds only warriors, then it's go time. Sending out a single axe certainly has merit. We might consider sending one in the most likely direction and send a warrior in the other, hoping to send a chariot not too long afterwards in the other as well.
I ran a test with 10 Mansas. Made contact after 10 turns. First skirmisher was built on turn 42. By turn 59, 4/10 had skirmishers. The 6 that didn't have skirmishers were all coastal, had concentrated heavily on fishing and workboats, and hadn't even started building a skirmisher. This is the kind of Mansa we should be hoping for.
Did you use AW and did you make sure the AI had made contact with a rival on same continent?
Mansa's scout did appear from the NE, so you may be right that he is on the east coast to the north. If we were to send a lone axe out into the fog, this might be the best direction.
Here's a first draft of a non-rush/axe-harassment scenario:
Put off second worker production for a few turns.
Put citizen on bananas, and work on a warrior 7 turns until copper is mined
Once mine built, switch to axe and move worker to chop forest.
Shortly before chop comes in, send one warrior out to explore in direction don't plan to send axe, if no enemy units are threatening
We should get axe and then warrior with chop and be very close to size two
Move worker to another forest
Grow city to size2 and begin a second axe to the point that we can pop rush or use chop for it (rather than second worker) if necessary, then switch build to second worker and move first worker to cows after he completes his chop
Once axe is off to harass, it might be smart to keep a warrior fortified in London to discourage AI forays.
In a couple of my test games, AI warriors did enter city limits with bad intentions, though much more often they go around. I know this was before 2000BC, but don't recall exactly when.