Generally i don’t need a midi offset, but i rarely use ableton as a master as i generally use a hardware setup with the computer just for recording purposes. However when i do have it set up for sync purposes – it seems fine without an offset – i know that ableton’s sync can be a little unreliable though… you should see if you can get the latency on your soundcard down – sometimes this can be the problem – i’m not sure what that alesis card is like for latency, but you need to try an reduce the latency as much as possible, and then use the ableton offset to make it sync exactly right
Regardless – 250ms is gigantic – even if you need an offset, it should be only a few milliseconds either way…
are you definitely using ASIO sound drivers?