Only played one game so far (4 player).
The player who started in bottom Right corner of map was landlocked, having great difficulty getting to ports.
Player who won gained fair bit of influence from overseas campaigns (and he was near a port).
So... does this mean we played badly?
Or the map does have problem?
What do experienced players feel about this?
During setup one can put nobles anywhere on the map, so setting the stronghold in the corner shouldn't be so important in regard of sea access.
As for the chances of winning without early access to the sea, I won't say a thing, because I played only twice.
I wouldn't say that the southeast is much better or worse than the other areas. The lack of access to the sea in the southeast corner is a drawback, yes, but there are two benefits:
1. The southeast is an extremely stable and defensible position due to all cities being immediately adjacent, and two cities not being on roads.
2. It's usually faster to snap up kingdom cities than foreign ones, so you should be able to jump out to an early lead.
The proximity and difficult terrain makes it very difficult to break into the southeast corner if there's any significant defense, and it usually results in the attacking player leaving something else open. If the other players have nobles gallivanting around in the foreign cities, then it's up to the southeast player to take the fight to their lesser-defended holdings. This may entail striking some bargains with the other players to tear down the leader.
There's a large amount of meta-game in the strategy for Warrior Knights. Getting out to an early lead and convincing people not to attack you can be an easy path to victory.
Of course, every board is different due to the razing of cities at the beginning of the game. I'd say that has much more of an impact on whether any given position is good than the ports do.