I failed once on lvl 8 too and because of Morgan too. so boring. as revenge, I tripled my reds (Scarlet, Kelile and Bold. only scarlett 60/70 and 8/8)
on level 10, I failed twice. always morgan upsetting me and worse tile too. I took my 3 reds plus Rigard and Melendor almost all full except Scar. on third try, I took like battle items, arrows, axes, bomb and dragon attack. I reduced Morgan’s life of about more than 300 pts, and a little Arthur and Guenevere. then, I threw 3 dragon, bomb and axes on them. hit them a little and when I saw they were ready to use their spec, I threw an arrow, they missed some heroes and hit some. after two hits using arrows, I threw last axes and arrows on them and killed Morgan.
Finally, I killed Arthur and Guen in the very end.
Hope that’ll help !