"math" wise, you'd have it right. But some of the rider effects on the attacks (such as some conditions, zones, etc) are not appropriate for all levels.
My general guideline is to adjust a monster no more than 4 levels. But that's just my own guideline based on how I see things go with my particular group.
For instance, generally, petrificaton doesn't appear until late heroic tier. and things like domination attacks might be at will abilities on high level creatures but a recharge 6 ability on heroic teir monsters.
Also, some monster effects that cause changes in terrain are 'tolerable' at higher levels because at paragon and epic the PCs have a greater chance of being able to fly/go invisible/teleport often/shift multiple spaces/etc. But by putting those same terrain altering effects at lower levels, you pretty much put road blocks for the PCs that they don't yet have the powers to circumvent.
Also, later level monsters have inherent modes of their own movement, like good flight, phasing, etc. heroic PCs will get frustrated as they have few ways to catch up with such creatures on a regular basis.
So, anyway... as said, math wise, you'd be fine. But it's the conditions and rider effects that come with the damage (conditions, condition inflicting recharge, zones, terrain alterations, the creatures movement modes) that would be out of sync
You could probably pick one or two and do it with careful consideration on effects, conditions, and recharge rates. But I wouldn't suggest just doing a sweeping change on all epic and paragon monsters.
