Umm yea. We don't use medium and hard encounters unless we want a push over. Most of our encounters are deadly or harder. No we do not optimize our characters. Almost all of our players have been playing for decades. Several of them are mathematical geniuses and well understand tactics very well (as they apply to D&D) and can intuit what to do when. We up the HP of many NPCs so that they live longer. And we try to avoid tactically stagnant combat, things move, they change and adapt.A dozen round combats not being unusual? We're talking 5e?
That sounds crazy to me, but I'd be really interested to see how that goes- always interested to see how different tables play. Can you elaborate on it?
The longer rounds are probably mostly due to the higher HPs, but that would be boring if the fights were not dynamic. We also often use waves of NPCs, as long as they bring something new and interesting to the fight. Again, not just a slog through HP or resources. Also, NPCs don't just stand their until they are dead, they act, and react and try to stay alive.