I'd just toss in there that as a general rule for me (only lvl 7) I'm not figting anything stronger than weaker than me.
No need to fight anything that says match, just come back later to it.

being weaker doens't mean heir army is alot weaker though ^^

it only counts on leadership

i can beat impossible armies with ease :P
it all depends on tactics and your choice of spells and rage

that may be true but at this point I don't suggest fighting impossible if your looking for flawless wins :)

depending on which difficulty
i would suggest to take all head on

your skill will imrpove faster this way

and get better understanding

on impossible you would not likely meet very weak armies;)

There lies your problem i think, you should really do the lyralo island, it gives you a new 'title' and with it a huge leadership boost, also i think swordsman and bowman become 'horde' then in the main castle (means endless ones for hire). I could be wrong on the horde thing, maybe thats later, but you should do the island asap, just charge it :-) or read some tips for the battle here on forum

1 ancient vampire can kill the turtle
else use 1 horseman 1 archimage

rest all shooters

move horseman in front of turtle

hold
use shield from archimage
and heal with priest or yourself

and shoot the turtle down

Yes--the Turtle is "do-able" at a fairly low level, as I found out last night (in my first game, medium level, as a level 4 Paladin. The Turtle looks much worse than he is.