For years, I battled my players on Magic Users and Illusionist. No one would play them because at low level, they can't survive combat. Of course, they can't. They aren't meant to rush headlong into combat. You need those clerics, thieves and of course, the mighty fighting man to smash whatever remains of the enemy after the Magic User has his or her way with them. Once a couple of spells are released, Magic Users should take a back seat to the action.
No one likes the back seat.
I even had trouble trying to get players multi-classing MUs. My players' opinion was that fighters fight, thieves steal and Magic Users use magic. And never the three should meet. Two of my players advanced a ranger and paladin to spell casting levels, but then never used the option because they believed it to be to unbalancing.
I was always a fan of Fighter-Magic User-Thief when I couldn't be a Bard under AD&D, and wanted my players to do the same.
In an effort to inject something attractive to the players into the Magic User classes, I tried some house rules. The only one seemed to appeal to the players was Counter Magic. Back then, I didn't have the whole thing codified like I do now, so it was a relatively unsuccessful trial run of House Rules.
Two other ideas struck me: Down Casting and Crisis Casting. They also turned out to be untenable.
Down Casting is simple. The character has a certain number of spells of certain levels. A fifth level Magic User has 4 first level spells, 2 second level spells and 1 third level spell. When Down Casting is in play, the Magic User can forgo his or her third level spell and convert that to 3 second level spells. They can take it a step further and convert a second level spell into 2 first level spells. Note that you get x number of spells based on the level of the forgone spell. I had thought this was diminishing returns, but it wasn't enough.
You can probably see how that didn't work. While we were play testing this rule, the 5th level Magic User Down Casted his 3rd level spell to two second level spells, then Down Cast all of his second level spells to first level spells. He then spent the entire combat casting magic missile. I am uncertain as to how many times that was, but he could have potentially put 36 magic missiles in to the enemy. I recall they ran out of enemies really fast.
I still think the idea has merit, but needs a different mechanic to prevent a magic missile MERV attack.
Crisis Casting was a little more successful, but also equally untenable. The rule was, if a Magic User has 10 or less hit points and is hit for damage, they regain memorized one first level spell. I had intended for this ability to make a spell caster more dangerous in combat, but it ultimately caused the deaths of several characters.
From a DM's perspective, Crisis Casting seemed to be a cure for any number of tactical problems. However, in practice, it made the Magic Users too aggressive. Instead of using Push, Jump, Spider Climb or Feather Fall to take control the tactical situation, most player simply unleashed another offensive spell. Usually of the type which didn't help them the first time. It could be that with limited spell slots available and combat being on the mind, they didn't memorize the right spells to make good use of the talent.
I'm probably going to try to reintroduce these option in my next campaign, but need to rethink each of them. I have the most hope for Counter Casting. What do you think?