I go for 8 seconds - seems to work every time!
As to the original 'problem' - it's next to impossible for anyone to react to your 10-second-from-the-end bid manually, so the item was probably bid for electronically by other equally switched-on snipers.
Thus, it would be the highest of the 3 bids that won.
By being the first of the 3 last-second snipes, you actually had a slight advantage over someone with the same maximum bid as yours. As yours was placed first, it would have won under Ebay rules.
But, I guess you didn't win. Not AS's fault for bidding a few seconds early but yours for not bidding high enough. IMHO!