That second half was some of the most exciting and positive football I've seen from Swansea in ages. I don't even mind the score because that half shows that this squad is capable of so much more.
Classic blunder in the first half - giving them way too much respect. Naive defensive tactics, too. You can't play physically in your own penalty box anymore because the opposition will go down on any contact, and nor can you play decent structured defence in your own area based on interceptions and blocks because it's too close quarters. Also, Saints were never going to play high balls from the wings, so crowding the penalty area only increased the chances of a handball (thankfully didn't happen), or blocked Rushworth's view. There's no benefit at all, only disadvantages.
It would have been better to play an extremely aggressive forward-line press with a compressed medium block / 2 rows of four in the middle third and foul the fuck out of them all day long. Take it in turns so the yellows don't come until the second half when you're looking to make subs anyway. It's a dark art but needs must. Disruption is the key to spoiling a pass-and-move outfit, kill the momentum. Probably Williams didn't want to do that because it's too cynical and because Swansea's defence are so slow. There'd be the obvious risk of a line-breaking through-ball to a fast forward, but that's nothing a well-rehearsed offside trap couldn't fix, not that the offside rule was enforced today.
Allowing them to play all their ball in the final third was suicide, but to come through after that first half with a 3-1 scoreline and a strong showing in the second half which made Saints look quite ordinary is very good.
Williams should keep Bolasie, buy a couple of fast defenders and play the forward line
@CroJack suggested (Bolaise, Pato, Patino, Cullen).
Also, re-invent Ollie Cooper as an aggressive #8. He'll bring ball-playing skills to a midfield enforcer role and can alternate with Allen, because Fulton is way off the boil this season.