One opinion about 4e that seems to be nearly universal is that combats take too long. This has always interested me, since at once I both agree with the idea yet also disagree.
Part of the problem I have with the opinion that combats take too long is that it’s comparing apples to oranges. Generally the comparison is implicitly made to earlier editions of D&D. However this neglects to take into account that combats have changed substantially in character from 2nd to 3rd to 4th edition.
One of the things that 4e does very well is the big set piece battle. This is largely due to the changes in the system that emphasizes the encounter, as opposed to a series of encounters. In earlier editions of D&D the big encounters at the end of the adventure tended to be anticlimactic, especially at higher levels. Usually the PCs ended up killing the Big Bad Evil Guy (BBEG) in fairly short order, especially if he was by himself or with only a few minions to protect him. This went double for enemy spellcasters since the PCs usually had fairly simple ways to negate his spellcasting abilities (Silence spells, grappling, etc).
The only exception I’ve ever seen myself is the penultimate encounter in a rather popular 3e module, but it required the BBEG to be able to spend 7-8 rounds of not being attacked in order to cast enough buffing spells to be a substantial challenge to the party.
As well, in previous editions, each encounter wasn’t necessarily a significant challenge to the party, but it was through attrition of resources (namely hit points, healing and spells) that eventually the party was in trouble for that last encounter of the day. In earlier editions encounters usually featured one monster of roughly equal level of the party, or several weak monsters.
Each encounter would take some hit points, require some healing spells cast by the Cleric (or judicious use of a Wand of Cure Light Wounds), and would take a few spells from the Wizard. However, the Wizard by mid-levels could be capable of doing enough damage to wipe out those weaker creatures and often those weak creatures would find it difficult to even hit the PCs (one reason I love minions in 4e). So those creatures are going down fast and also because they have a tough time hitting, their actions are usually resolved quickly. In addition, most monsters only had one or two attacks at best (and certainly only cast one spell per round).
Against a single relatively powerful creature or a pair of them, the monster turns would go very quickly (again due to a lack of monster actions) and since the entire party would be ganging up on one or two creatures, they’d drop quickly.
In fact, if you ran 4e encounters the exact same way, with multiple creatures of significantly lower level…or a single creature or pair of creatures of roughly equal power to the party, I think 4e combats would go almost as quickly as earlier editions went.
The problem with this of course is that 4e has changed the game as far as resource management goes. Although each class now has its share of Daily powers, the spellcasters have fewer than they used to have. This is of course balanced by the existence of At-Wills and Encounter powers. In addition, the party is no longer restricted by the Cleric running out of healing spells although someone will eventually run out of Healing Surges. Everyone does less damage generally speaking than they did before, which means that an encounter against multiple weak creatures (minions) or a single or pair of Standard creatures will be hard pressed to impact the PCs at all. They can probably get away with just Encounters or At-Wills, and one or two PCs might end up spending a Healing Surge.
This is also why wandering monsters don’t really work in 4e (and their inclusion in official 4e adventures is more to do with tradition than it being a good idea).
This I suspect is why a post about doing 4e old school style, Sly Flourish wrote that you’d need to do some house rules in order to make it work.
1. Contingencies...all the different situational modifiers.
2. Problem increases at Epic/Paragon
3. 'slow' encounters usually compared to 2nd ed and earlier.
My final point would be if you’re having fun, does it really matter how long the combats take? Recently my group had a big end-of-the-campaign battle that took the entire 3.5 hour session and we had a blast. Similarly, the Chatty DM also had a similar experience (although he initially was annoyed at how long it took).