Sorry but prevent clustering doenst mean fixing the algorithms. Clustering is possible and in 100 or 1000 dice rolls it doenst hurt. The problem is that the ingame Combat has no 100 or 1000 rounds per fight.
Which means you looking for a "Pseudo" Random Generator like in E-Sport games like LoL in which you have Critchance on Items but the algorthims flattens the extreme values. So its nearly imposssible to crit 3 times in a row with maybe 30% Critchance but on the flipside you have no 4 or maybe 5 Hits without a crit. Its a more "realistic" approach for low Numbers.