I've taken a shot at making a bomber-only level that doesn't solely rely on bomber timing to create the difficulty. I guess it's rather easy to figure, but hopefully not entirely trivial.
I remember a well made but fairly hard Cheapo pack that got posted here a while back (forgot who made it, though) that had a dirt set level with nothing but bashers that was not at all trivial and actually quite fun. Used the non-even terrain of the set very, very well.
What you're referring to might be the pack 'Why bother?' by the Purpletraitor (and drumnbach?), specifically the level 'Mount Bashmore'. "A while back" is quite an understatement though.
That reminds me though that I've still got to have a thorough play-through of this pack, because back in the day these levels still seemed pretty daunting to me.
EDIT: In this pack, there's also "...but, but, but...?!?!", a builder-only level.