I have 3 starred max TH8s with barch before (lv6 barch of course) and considering the fact that as a TH8 I have never had trouble 3 starring pretty much any other TH8 fully maxed out or not, you are @2000 cups, TH9 play ground, just yesterday I 3 starred a TH7 with that mantis layout using giants arch and gobs (no spells used) the game is made so that attack can always beat defense, and there are lots of good attackers @2k cups, esp if you want to defend as a TH8, TH8s belong below gold 1

, being at crystal as TH8 and trying to win legitimate defenses is like a TH7 in gold 2 when a TH8 finds him it = game over for the TH7 lol, but if you care most about defense wins rather than anything else you should use a trap base, clan leader of extreme eight snufflebuns made a base that won defenses for TH8s up untill masters league (which is amazing) I honestly think it's the best base ever made purely to win defenses, Snuffles retired now but you can see his base here:
https://www.youtube.com/watch?v=82OuLtPLsO8
either Kingzzz or Young Wills base will definitely get you defense wins, Denny Huang (previous clanmate) had the same layout as Young Will and actually won 17 defenses and actually got into master league from defenses!!!, any good luck finding a base if you don't want any of these
