The point is - last season we played one up front. This season we're playing 1 up front. A 1-1 rather than a 2. Daffy is as much isolated as the striker was last season. The only differences being that: 1) Ade played last season as the lone striker 2) The support from Modric/VDV has gone and been replaced with Sig/Dembele/Dempsey
The problem is as then, that although Daffy has been scoring, he doesn't play the lone striker as well as Ade - so AVB changed the team to suit his inclusion - ie we played narrower so Bale/Lemmon could get close to Daffy to support him as well.
All in all not so much AVB's fault either as we'll never know who would have stated had Ade joined earlier and been fit from the off. Now Daffy has scored a few and it then makes it 'iffy' to drop him in favour of Ade (much the same as dropping Friedel when he's on form for Lloris would look strange - although I think more accepted given the futures argument). Then Dempsey/Sig (so far) aren't as effective as VDV was then in support.