Yeah there are many monsters that need morale buffs when they become bosses (e.g. imps) so that they don't run away. All pets also need morale buffs. Additionally some mobs aren't suited to be bosses. The Scarabus, which you mentioned, should have its suicide ability tied to its morale rather than firing off randomly as it does now. If you give it a morale boost and make the boss's explosion much bigger, it'd actually be a decent and pretty cool boss. It could actually serve as an excellent and very dangerous scout with a very big morale boost: if it gets close to the critical NPCs, you're screwed.
But there are still bosses such as orc shamans who just stand there, slowly firing poison at you and generally being ineffective.