If you look at City and Spurs, the two highest scoring sides in the league last year...
Spurs had Kane scoring 25, then the next highest scorer was one 10, then the 3rd on 6.
City had Aguero on 24, then Iheanacho on 8 and De Bruyne on 7.
I think it's massively unrealistic to expect anyone who is not an out and out striker to score 15+ goals.
Spurs built their title run based on their defence not their attack.
Manchester City a few years ago had Aguero & Dzeko both scoring 20 +
We had Sturridge & Suarez scoring 20 +
Chelsea with Hazard & Costa
Leicester with Vardy & Mahrez.
If you're playing a system with 3 lads up front, don't expect to finish any higher than 8th if two of your 3 attackers can't score more than 15 goals in all comps.
Coutinho & lallana aren't fowards, they're midfielders. That's the point I'm making. Lallana is a good option, but he shouldn't be in our front 3. He's got good control, retains it well, but he doesn't score often enough to justify starting there.
Put Sturridge up front, with Origi one side, and a lad with numbers the other and we'll be in business.