I'm looking for mechanical options that might speed up the time it takes to get through combats. The issue is not how long the players take on their turns. The issue is not looking up rules. The issue is not the battlefield grid we use or the miniatures and how they move. The issue is not tracking initiative. The issue is not the number of combats per game session. I have received lots of advice about these issues. As I stated previously, it's all great advice but doesn't help, as these are all things that have already been streamlined.
I think the issue is that the party (made up of an evocation wizard, a cleric of war, a gnomish warlock and a paladin of vengeance) could be falling behind in their damage dealing somehow. They don't hold back their big attacks, so I know it's not a matter of them only poking enemies with cantrips (though the warlock does use cantrips frequently, but I think that's to be expected). There are plenty of evocation spells flying about, smites going off and the cleric of war splitting his time between cleaving things with his sword and inflicting wounds upon enemies.
A recent battle had them squaring off against two shambling mounds (around 136 hit points apiece) and a cleric of Moander (who had about 70 hit points). This battle somehow took around an hour. This isn't even a big boss battle or anything (the group is attempting to fight their way into the Pit of Moander in the Ruins of Yulash in the Forgotten Realms). And it wasn't due to the fire resistance of the shambling mounds, as the evocation wizard has the ability to bypass it completely. So, I'm just confused.
The battles don't always take forever, though. I threw lower level enemies at them prior to them entering Yulash. They obliterated the opposition in the first round before the enemies even went. Combat over in less than five minutes. So, it's quite jarring to go from five to ten minute combats to things that can take over an hour due to hit point inflation.
I mean, I expect there to be some increase in time, but not that much. So, any mechanical advice on how I can keep things up to speed while still keeping the dangerous enemies deadly?
That seems really long for that fight.
Paladin of Vengeance should be using Hunter's Mark for his standard attacks at 13th level or possibly haste and his smites. If his strength is 18 or 20, he should be averaging with a longsword 12 to 13 damage a hit plus smite damage with two attacks per round.
The evoker should be doing one fire bolt cantrip minimum for an average of 21 fire damage or maybe a chill touch for 18 necrotic damage per hit. He should spike this use of spell slots.
Your warlock with hex should be firing 3 eldritch blast beams for an average of 13 to 14 per hit and up to 39 to 40 per round.
The cleric of war should be casting bless to ensure the others hit and adding a sacred flame or meleeing some for 10 to 15 points per hit.
The party's damage potential per round is:
Paladin 26.
Warlock: 30 to 40
Evoker: 20 to 30.
Cleric: 10 to 20.
You're looking at about 86 points per round without blowing off their big stuff. Against 342 hit points, that's about 4 rounds of combat. Is it taking a lot longer than 4 rounds against something like two shambling mounds and a cleric of moander? Maybe the cleric is doing some healing? Your party isn't using chill touch to eliminate healing.
There are certain things party should do to optimize for combat. If an opponent has healing or regeneration, you absolutely need chill touch to slow healing down. You can still win, but it will slow the fight down if the opponent can regenerate or heal.
The cleric bolstering the party with bless is often better than casting spiritual guardians. He should be hitting with his main weapon and bonus action in big fights. Or casting something like spiritual weapon to add damage while he is doing other stuff. A 4th level spiritual weapon does 2d8+wisdom modifier damage using a bonus action. So if he's hitting with his weapon with bless boosting everyone. He can do with a one handed weapon 2d8+str or dex and 2d8+wis for decent damage while healing and such.
Seems your group should be able carve through that many hit points in 4 or 5 rounds if using optimal tactics.