I've noticed this in several RPGs, including CV Lord of the Dungeon and Bard's Tale 2.
Fighters are usually good to have around early on, but before long become all but useless. When I was killed off by the Dark Lords in LOTD, my 52nd-Level Fighter was completely useless, even with magical weaponry. In fact, in the lower dungeon levels, only spell-casting characters are of any use.
The main problem is the fact that fighters don't really improve much, no matter how many levels they gain, except in Hit Points- which isn't really any good if you can only stand there and get killed.
For example, in LOTD, with appropriate weaponry, a fighter can only hit twice in a single round. Even if you reach Level 50+, this never changes. However, higher-level magic or cleric spells allow a high-level caster to wipe out entire groups in a single attack.
Compare a Ninja to a Monk. With enough money, a Ninja might start with a better Armor Class, and can advance more quickly through the levels.
However, something quickly becomes apparent. When you surprise Undead, the Monk, like a Cleric, or other cleric-spell using classes, is given the option of trying to "Dispel" the monsters. The Ninja, like all Fighters, has no such option. What's more, he can either, with the appropriate weapon, strike 2 normal blows, or only one "Critical Hit." The Monk, on the other hand, ALWAYS has the option of TWO such hits!
Once you've gained some levels, you notice that the Ninja, like all Fighters, only gains Hit Points and a better chance "to hit" an enemy (but so does everyone else). The Monk not only gains these things, but also clerical spell use. These can heal, cure poison, paralysis, raise the dead, and do mighty damage against enemies, not to mention gaining control over even some pretty tough monsters. What's more, the Armor Class improves constantly, becoming by far and wide the best of any character class, while the Ninja doesn't see much improvement.
The Scout can increase surprise abilities, but again, so does the Monk, or Ranger, and with all of the other advantages those classes have, too. The Phage, the magic-using equivalent of the Monk, is also better.
In the RPG I programmed (old prototype) for the Commodore-64, I addressed this by giving the Fighter more strikes/round as he increased in level, more damage/attack, and certain things to allow certain, limited "spell-like" effects, although very limited. In short, adding Fighter-Levels to your tri-classed character made sense, especially for Hit Points.
Are there any other games, especially the newer ones, with this problem?