imo drop chance should increase still if you're within xp range of your party members.

Think about it, if 8 players in range (which is an unlikely scenario to begin with) made drop quantity increase 100%, that's only 2x the drops you'd get solo, split among 8 players. It'd still be better to farm solo for drops overall, but it wouldn't remove literally 100% of the incentive to farm in a party.

xp gain should also increase but only if you're in range of your party members. I also think it should take MUCH longer to get 99...