I disagree, Pasha, especially regarding the swamp...
I personally cleared level 113 with the following troops: 20 lizards (not upgraded), 2 vipers, 47 gnolls, and a single butterfly, plus a dwarf with 100 health...
It's done easily and simply, without any fuss. On the right side, pull everything down, losing 1 butterfly (otherwise, they won't follow). On the left side, absorb the counterattack, losing some butterflies, and then attack with everything. After that, move the lizards to the upper left corner and eliminate the remaining enemies with 8 shots...
The vipers and lizards remain intact, the gnolls suffer losses of 15-20, and the hero gains 4 levels and 2 attacks...