A hitpoint at level 2 is not the same as a hitpoint in level 7 in 4e. So if you are going to be using monsters outside of the 4-5+ PC level range they need their hp upped and their damage increased IMO. I'd also lower their defences by some scaled amount. This will at least allow some attacks to hit. The same goes for monsters well below the PC's level range - increase defences, lower HP (even to minion status), lower damage, increase attack values.
Very good point, doing the latter works well, and it's a pity that 4e does not include a mechanism to do the former. If you turn a Level+8 Standard into a Level+4 Elite, the doubling of hp means it's still a grindy combat.
Hmm. It sounds like the trick may be to turn the L+8 Standard into a L+4 Elite, including increase in damage output, but then half the hp (and award 2/3 of Elite XP). This ought to work pretty well, although it's still a fair bit of work, eg the Monster Builder doesn't increase damage output when you Eliteify critters AFAICR.
Thanks though, this is useful advice.