It took me about 20-30 reloads [editor's note: this seems high] each before
I could beat Improved Irenicus, Eclispe and Ascension on Core level.
Improved Bodhi and Kuroisan both took a brave few reloads as well.
Improved Maevar, the Guarded Compound and Twisted Rune were only easier
because I tackled them after the Underdark. I originally tried to get C
Fury early on but got an ass kickin, then had to reload!
10 out of 10 in my books.