I'll go ahead and jump in this thread specifically about the high ground "I Win button" that is currently implemented. I'd like to see 2 changes myself and the 2nd might not be popular.
1. Personally I think Adv/Disadv needs to be removed from the equation completely with regards to height's influence.
2. Higher ground should increase the range for physical attacks(arrows/bolts/thrown items). This should NOT apply to spells.
Imo increased range is the only benefit higher ground should have and that is because that is just plain how gravity works. A spell's range is basically a sphere centered on the caster that the spell can reach before it fizzles out. Higher ground would have no affect on that. I feel this would still make higher ground advantageous for any ranged toon since by its very nature it limits an enemies access to you.