First off, behest is a group event so it should be really hard for someone to do solo.
Secondly, learn to read the popups instead of just pushing buttons.
Leves now work like this:
1 Star - Monsters are the recommended level for the leve.
2 Stars - Monsters are 3 levels above the rcommended level
3 Stars - Monsters are 6 levels above
4 Stars - Monsters are 9 levels above
5 Stars - Monsters are 12 levels above

So, take a leve with a recommended level of 20:
1 Star - level 20
2 Stars - level 23
3 Stars - level 26
4 Stars - level 29
5 Stars - level 32