there's just a few things you shouldnt use if you find the game too easy:
1. elite skill
2. pve skills
3. pvx (worst of all, make your own builds from scratch, like i do now)
4. heroes/7 heroes
only these 4 would make the game much harder in HM already, unless you remember pvx builds which you can use and edit, but then still isnt yours
pvx was first made for those who like to share and the ones who liked to get inspired, but now people just go pvx and copy/paste templates, thats NOT playing the game, thats copying what others do.... find your own way in life... AND in GW (and perhaps other games too)
use SF in your 7 hero team, that way it wont be as useful, as you play with your heroes
i can think off more ideas to make it harder, like "use half max armor" (and without runes/insignia's) "no weapon upgrades" and "no healers" and such
for me, i just enjoy the game with my own made builds now, got inspired by existing builds which i heard of, and some i didnt even see, and i try to make the game fun by using all my heroes (all as in whole team of heroes) and in the future i'll use more heroes like derv and such (if they ever improve hero's melee AI)
unlike those hardcore whiners, i enjoy the game, and while waiting for cantha: WoC, i'm doing stuff i like to do, or try to achieve what i want to achieve, and not looking at anyone's builds
for example, i never used AP (and never will)
speaking of which, make AP work only for assassin skills, thats what it is for imo, thats half the problems of elitism being solved i think