Last night the party fought a dragon.
The bard has vicious mockery and psychic lock.
The bard also had powers (some multiclass) that:
a) healed for 6 hp each PC who hit the dragon.
b) granted each ally a +6 damage on damage rolls against the dragon.
c) let him and one ally roll twice for every attack.
The dragon had a -4 penalty to attacks every round (except for the rounds when the warden/giant slayer climbed on top of the dragon, and the illusionist used some power that incurred a -5 penalty) and kicked the total penalty to -7, or -9 to attacks against anyone other than the warden.
The ability to stack so many penalties, especially against a solo, feels radically overpowered and crippling. Are these penalties supposed to actually stack like this? Are there things I'm missing?
Looking at your rough draft the creature was pretty formidible, but complex to run. The minon power intrigues me thouh, it might have been better served with the deathmaster template. have the dragon start with (4) minions that distract the party at least a little, and instead of the tearing off limbs thing consider a power like the Berbelang to duplicate itself.
Those ideas voiced, like level solos I have seen get pummeled if they have few options. This party was able to stack penalties to hits to crippling effect. Where were the dragons +5 saves? and what about flight. I have a party with the rogue who used walking wounded a lot to make foes fall, when he used it against the griffon riding ranger though, he realized that the griffon could grab him or a fellow in melee, then fly up taking the fall and dropping the party member.
Bottom line is, creatures with few options are easy to cripple for 5 foes coordinating their efforts. (especially five power gamers). Your dragon needed an option that either gave it a way to recover, or that didn't require a to-hit. auras which several dragons have particularly the red, can do at least a lttle damage without rolling, and the white is good at making the terrain around it difficult.
Here's one to try next time: Have them meet a gargoyle with the demonic acolyte template. It can be advanced to the appropriate level, and have allies that don't seem too threatening, say goblins. For his first action have him summon his allies, and then turn to stone. resist all 20 for all the minions as long as they stay close. The heroes will have to use at least some resources/effort to do 21pts. with a blow enough times to drop each ally, even if they are minions, it's a challenge at low-mid levels, and then the gargoyle can revert to normal and attack when they are, (at least a little) exhausted.
another favorite of mine is the grey slaad in the MM. It could cause at least one condition effect to backfire on the rogue/bard or whomever. If you make a solo slaad with a lot of hit points, it can become a long night for the healer.
vampire lords have some well known weaknesses even in fourth, but if you dominate a foe, it will let you blood drain. (no coup d'gras because dominated targets are dazed, not helpless). With a dominated heroe, you could rule that he will let the vampire do blood drain if it seems nonthreatening. In our game, it bloodied the hapless rogue, so blood drain recharged. The vampire lord spent his action point and did it again nearly killing him.
I am quite sure others on here could come up with other 'evil encounters' maybe WOTC should put out a book of them.