We did the same with klassen and sandros (basically stopped playing them without giving them a chance) and look what happened to them.
Horses for courses.
Against Arsenal, we're going to need pace on the counter.
Personally, I'd go with DCL, Walcott and Bolasie, with Gylfi dropping into midfield alongside Gana and Davies (though I think he'll play Schneiderlin instead of Davies).
I'd have Tosun ready to come on from the bench if required.
However, I also see the sense in having Tosun start for his hold up play, but that only counts for anything if Walcott and Bolasie get up alongside him.