" ... not nice ... "
Heh, why of course !!
I was just going by a tight rules basis.
The wotc 4e CO-board isn't really interested in what the monsters do.
It is possible to put a Class Template on any given monster,
and then you have an Elite (or Solo) that has
some of the mojo the PCs have.
The other stuff to do is use lots of Traps within an Encounter.
The trap functions as a monster, in terms of the exp budget.
Then it's just a matter of how much screwy stuff happens to the party,
while the monsters know all about it.
Problem ... sooner or later the party catches on to Traps being something
to pay attention to. Then they almost don't work anymore.
High Percept or Thievery or Dex builds can handle them right off the bat.
But the rest of the party has to come up with a Process to figure out how to handle.
And later you nail them with a Two trap combat ... or More
I'd save this for the toughest combats.
Even so, the PCs are still supposed to win.
You have to hit them with a Too Hard combat,
to make them actually have to
retreat.
That word doesn't exist in 4e
Seriously scan the whole text of every 4e book.
You won't (will) find that word.