Lovely finish from Ramsey, but otherwise Arsenal's lead is totally undeserved. Spurs totally dominated the first half hour, and Arsenal's goal was their first shot on target.
Danny Rose in particular has been excellent. Nobody on Arsenal is tracking his runs until he gets to the fullback, which means he's always the out ball. The stat that shows the flow of the game is that Spurs have had 8 throw-ins on the left side: they keep attacking down that side through Rose, but Arsenal keep putting the ball out of play.
For Spurs, Alli and Eriksen have underwhelmed. Alli is overdribbling, trying to beat 2-3 defenders several times. Eriksen's positioning has been very good but his final ball has ben poor, and he's wasted a couple of free kicks in dangerous positions. Dembele has been very good, the best midfield player on show.
Welbeck has played well, his strength and pace gives Arsenal a different dimension. Alexis has been totally anonymous; he's mostly put in a shift defensively on Walker (compare how much space Walker has been given with Rose on the other side), but he's done nothing going forward.
Arsenal's issue tactically is that neither their CBs or their two CMs are especially good passers. They miss Cazorla a lot, and even Koscielny, who is a better passer than Mertesacker and Gabriel -- without them they have no one to spread the ball around, distribute play, switch the point of attack, bring the ball out from the back, etc.. The result is that Ozil has to drop too deep to get the ball, often picking up the ball near the halfway line where's he's a lot less dangerous. When they can get the ball with possession in the final third they look dangerous, but they are struggling to do that.