There's been a lot of talk about Mane's goal drought this season. The type which "wouldn't be tolerated at Liverpool" (even though he ended up with very positive numbers in the end)
You might want to check out Lallana's last 2 seasons at Liverpool. In 14/15 there were 17 consecutive league games where he didn't score. In 15/16 there were 22 consecutive league games where he didn't score. (Figures include occasional games missed through injury)
While people generally acknowledge Lallana doesn't score enough, nobody was calling it a goal drought.
It seems like Mane is judged more harshly because he sets higher standards for goal scoring
Yes, players who very rarely score do not suffer "goal droughts" they just don't score very often. It's only really used to describe players who are expected to score on a regular basis.
(So Danny Welbeck hardly ever scores, but nobody says he is suffering a "goal drought" they just say he's a bit shit.)
Players like Mane, attacking forwards who don't usually operate as out and out strikers, will often go through patches of scoring regularly. We saw both Coutinho and Firmino score in clear spells last season. If you have enough of these players, and these spells are well spaced (so you don't get everyone peaking at the same time) then that's great for the team.
The important thing is what they do when they are not scoring goals. Lallana, for example, is not a prolific goal scorer, but he was one of the more consistently selected players last season because of the other things he does. So long as the team wins, so long as someone scores, what is more important is that players contribute with pressing, with passes, with assists and with movement off the ball.
Mane's goal return of last season would be a very solid return for us if he repeats it this season. What is vital, though, is that the team as a whole scores more goals, not that any individual player racks them up consistently over the season.
We expect players to score more often the nearer they play to the opposition goal, which makes sense. So the burden of goalscoring falls mostly on the striker/s, with the wide forwards and no.10 contributing next. Again though, so long as this group are collectively adding goals, it is of no importance which player is notching them up.
In fact it is more useful to the team if these goals are shared out. Firstly because this means the team is less reliant on the form or availability of a single player, but also because it is harder for the opposition when the threat is more widely distributed. If we close down that dangerous lad on the left, the no.10 gets a bit more space, and if we account for that then the guy on the right has room to run into, etc, etc.
Further back, it's about chipping in. Often these players (particularly centre backs) will get goals from set-pieces. It's not expected of them or a major part of their role on the pitch, but the more they can bring to the table here, the more value they add to the team. A great centre back who never scores (like Carragher) is always more valuable than a merely competent defender who can get five goals a season (like Skrtel) because when there's a trade off at the other end, it usually costs more in goals conceded over a season than even a relatively prolific centre back is likely to score for the team.