anyway the fable about using less troops before going into battle to get more xp isn't working
i have tested this in impossible mode with mage
first i used like
10 horseman 15 inqi 10 royal snakes 3 alchemist
and after i only used 3 horseman
in both cases i won and in both cases i got 25xp
to kill the turtle is very easy without any losses
use fire dragonfly
let it use haste(get the scroll or spell last hero)
get 4 ranged units
make the firefly stand in front of turtle with defense
cast last hero on it
let i die and keep casting last hero(the turtle will always attack the firefly and your ranged units should take this one real easy without any losses:>
(USE inqi's to ressurect the fireflies)