I've found some charts online that have the damage for standard monsters, as well as minions. However, how do you calculate elite & solo monster damage beyond that? Is elite damage output doubled from the standard, while a solo is quadrupled? or, something else?
Most of what I've seen online is like this - which is great.
http://slyflourish.com/master_dm_sheet.pdf
Don't multiply damage.
Elites generally have two at-will attacks per turn, each dealing regular damage. Often they have a double attack, or make a basic attack twice, or use an attack on a reaction that commonly comes up (eg when attacked, when hit, when missed, when damaged, etc). Some of the old elites (eg the original orc chieftain) fail at this and do
not have an extra attack, turning them into a bag of hit points. A goblin boss in Keep on the Shadowfell, by contrast, did this correctly.
According to the official rules, solos get three at-wills per turn, but one at-will does +50% damage (as a recharge power), so they basically do 3.5 times the damage. However solo design is often poor, and there's numerous good solos out there too.
Solo dragons in the Monster Vault and later usually have a bite attack that deals +50% damage, and an option of two claw attacks (regular damage). There's usually an immediate reaction attack for if it's hit, flanked, or something like that. Finally, dragons have Instinctive Attack, which gives an extra attack (which if lost can remove a daze or stun effect). So the requisite 3.5x damage over a turn. Older dragons often could claw/claw/bite as a standard action and had an immediate reaction attack too. This wasn't strictly
worse (except the damage values usually sucked) but newer dragons have Action Recovery and Instinctive Attack, both of which protect the dragon from action denial while the latter still gives the dragon an extra attack.
Many solos might have a double attack as a standard action plus two minor action attacks, but that means the solo lacks mobility. (The purple worm does something like this.) Cryonax, a super epic solo by the writer of Sly Flourish, has an at-will attack that simply dishes out
five melee basic attacks. Ouch. As a solo is basically five monsters, that's a pretty popular way of handling a solo.
Some solos even have multiple turns per round (and a few elites too), so such a solo might have two attacks per turn, but that's basically four attacks per round. I've seen at least one monster that gets one turn
per opponent per round. And let's not forget the beholder. It gets two attacks per turn, but one extra attack whenever an enemy starts near it
even if the beholder is stunned! Against a typical party the beholder gets seven attacks per turn.