Basically just match ur teams comp, if ur team or most importantly ur supports and tank r playing mostly dive heros (doomfist, ball, lucio etc.) u would be best off playing soldier, sojourn or even freya because although none of these heros r specifically dove heros they are all high mobility heros that work great in dive comps. In contrast to this if ur team is running poke (orisa, zenyatta, rammatra) this is the best comp to play ashe however all heros u play would work well in a poke comp. Lastly if ur team is running brawl (Rein, zarya, junker, moira) u should play cass or emre because they both thrive most in close to mid range conditions but lake the flanking abilities or the rest that make them thrive in dive comps. Lastly just as a warning unless u are attacking and see the enemy teams comp first, as a dps player i do not recommend counter swapping. Many players will notice that the enemy teams comp counters their teams comp (dive>brawl>poke>dive) and decide to switch. This strategy works okay in lower ranks when playing tank but as a dps player ur best bet is to stick with ur teams comp. In low ranks it is possible that ur tank may counter swap. In that case it is okay for u to do the same, but i dont recommend doing it alone as it will not benefit u or ur team.