Buff spells are powerful. Buff spells are almost necessity level powerful, to the point that clerics and druids are arguably better classes for straight up combat classes and spell casters in general are always considered top tier. However, I’ve noticed that a lot of combat works like this…
DM: Alright, you can see through the door that there are six orcs and an ogre. They all look ready for trouble.
Cleric: Ok, before we go in I cast… Shield of Faith, Bull’s Strength, Divine Favor and Bless.
Wizard: I want to cast mage armor, shield, and protection from evil.
Cleric: Ok, now that we’re all buffed, we go in.
Every single time. That’s multiple actions taken with the enemy in sight (and therefore, presumably, while the enemy has the opportunity to be getting ready as well) and the DM regularly lets them do so without consequence. I think most DMs let it slide because they know that those characters need those buffs up to be at their maximum effectiveness, but that also throws the balance of them out of whack. This brings me a point that has become a standard DMing philosophy: Conditional Power Needs to be Conditional. If you need to cast four spells to be at maximum effectiveness, there should be no guarantee that you will be able to cast all four of them before combat starts. In fact, I’d be willing to bet that the casting time is part of the how the spells were intended to be balanced.
Let’s look back at the situation above. You can see that there’s a threat in the room, so you cast your stuff. In the safest circumstance, your rogue has cracked a door and peeked through it while you cast your spells, but those enemies aren’t statues waiting to be activated. These are spells that usually have verbal components, so the enemies on guard should have a chance to hear you casting them and interrupt. Buff spells are a lot more reasonably powered when they might take one of your actions in combat to cast them, or when you have to decide between casting Bull’s Strength and swinging your mace. Which brings me to point number two: If something takes time, it should have a chance to get interrupted.
Here’s another thing that players do that may just be a little on the strong side, but only because players are usually given infinite time to use it: the wand of cure light wounds.
Bear with me, because I know that calling a wand of CLW overpowered might seem a bit weird. I never would have thought about it until someone broke it down. A wand of CLW with 50 charges heals an average of 5.5 HP a charge and costs 750 gold. That’s an average 3.6 health per ten gold pieces. The next level up is a wand of Cure Moderate Wounds. That heals an average of 12 HP per charge with 50 charges, for 4,500 gold. That’s 1.3 health per ten gold pieces. Now, theoretically, the balance there is that you get more healing in a single charge and that’s great when time is a factor, but your cure wand is usually much more for post combat triage where, again, GMs give the players an unlimited amount of time to use them up without any risk of interruption. So, think about this in the context of a group of level five adventurers for a second.
Let’s say that your party of fighter, mage, thief and cleric have all taken damage. The fighter’s down by twenty hit points, the cleric by fourteen, the mage by seven, and the thief by two (lucky rogue). That’s going to take, on average, 9 rounds of cure light wounds to get them up to full. That’s a full minute, usually right after a fight that should have made all sorts of noise for other enemies to hear, and yet they never seem to get interrupted.
Which I think brings me to my final point. Dungeons and battlefields are dynamic situations. The PCs should get interrupted, ambushed, hassled and harried by their enemies. I’m not saying they should never have time to rest, what I am saying is that they shouldn’t always be secure that they can spend forever preparing for the next room.