I think the folks who are suggesting a change of game mechanics are on to something, though you may not need to do anything so extreme as buying new rules sets.
Many of your concerns involve using spells and abilities in ways that I (and nearly everyone else) find "normal." The very fact that these spells exist in the game suggests that they should be used in conflict. And let's face it: most of the spells in the PHB are combat-oriented.
You could:
(a) Remove some or all of the spells from play. House-ruling these spells out might be a useful solution (though you'll need to have a heart-to-heart with your players to make sure they aren't upset about the change). Or, perhaps you could implement the
Recharge Magic variant listed in Unearthed Arcana. Make spells like
entangle take a looooong time to recharge so they characters might not be able to use it again right away.
(b) Tactics. Others have mentioned it, but it's fair to say that if your party uses a certain tactic, then bad guys will hear of it and use it, too. Yes, it's circular. Welcome to "real" life. Emulation may be the sincerest form of flattery. But consider this: all of today's kids watching "reality" TV shows are learning that the winner is often the person who lies/cheats/steals/manipulates the most. Why not throw in a few NPCs to appeal to the character's "good nature" and ask them to prevent some kind of "moral decay?" Once the players have had a taste of their own medicine (or worse) they may willingly participate in efforts to fight honorably.
Another thing to consider is that you might not be having enough combats in a given time-period. Do your players have enough time to rest after each combat that they're back up to full? Why not hit them with four orcs (nothing special about them, just four orcs straight out of the Monster Manual) so they buff the heck out of themselves? Then, after that, let the "elite" orc guard come in and fight them. Uh oh... They've used all their spells on a combat that didn't matter. Now they have to fight harder with fewer resources. Perhaps they need more of a challenge to help them scale back some of their tactics?
(c) Implement the
Reputation rules in Unearthed Arcana (or roll your own, since what's in the book is fairly abstract). Let's face it: we always hear about how adventurers are supposed to be disliked by the general public. Why? Maybe it's because they have a reputation of fighting dirty. If your PCs' base of operations isn't some Old West style town, them walking into a tavern fully armed and armored is likely to result in a response akin to, "Black Bart is here! Everyone run!" The bartender will not appreciate the loss of business, and before long, you'll have the local constabulary asking your PCs to remove their weapons or get outta town.
Once the PCs have been run out of enough towns, they'll start to get the picture. But if they need more help, what if Lawful Good churches refuse healing to folks who regularly slit the throats of helpless opponents? Wizards refuse to sell them a new magic wand because they don't want to be associated with "mindless killers."
If enough baddies run away from the PCs after they've flown into murderous rages, slaying everything they see standing, isn't it possible that the local band of orcs will try to form an alliance with the goblins? Or the trolls? or the dragon outside of town? or...? If the bad guys are feeling seriously threatened, and the PCs have a reputation as ruthless killers, they may decide that all the tactics in the world won't save them. When in doubt, use attrition. You have 5 guys, I have 100. I'll just have my guys
aid another on a few big brutes, grapple you, wrestle you to the ground, and then slit
your throats before you can kill us all off.
* * *
You might even think about combining some of the above solutions. Imagine for a moment that you're an adventuring party of middling success. You've looted a couple of ruins, slain some evil orcs, and rescued the mayor's daughter while managing to amass a respectable fortune and groupie following. Then, from the next town over, you hear news of a new adventuring band. These guys don't play fair. They
paralyze folks and slit their throats,
entangle foes and cut them down with bows and arrows despite their cries for mercy (this might not be true, but rumors aren't always true, are they?), shoot fleeing combatants in the back, and walk into town fully armed and intimidate the populace into giving them free room and board and free supplies (again, maybe not true, but rumors can play hell on a reputation).
Suddenly,
your honor is at stake. Your groupies aren't so sure you're as heroic as your own stories about yourselves indicate. The local mayor gets jittery around you, constantly eyeing your "peace-bonded" weapon. Merchants are suddenly "closed" whenever you venture over to check out the new wares. And you notice a group of the local militia seems to be keeping an eye on you from a "safe" distance.
Those jerks in the next town are ruining this heroism thing for you! What are you and your buddies going to do? Why, head on over and bonk that other group of "heroes" on the head. Sure, you'll be as honorable as you can, but you'll be mean and nasty and tell them that if they don't shape up, you'll come back to kick their cowardly hides! So, whallop them, leave them bloodied and bruised (but alive), and head back to your own home base praising your efforts and singing songs about how you gave hell to the cowardly adventurers the next town over.
