Strain does determine melt. As mentioned earlier: Melt is not an indicator of potency, but of the presence of oil soluble terpenes, which are responsible for part of resin flavor. Indica strains have been selected for a thousand plus years to make good hash, and that is still very true to this day. Cannabis sativa hash is somewhat of a new product, as traditionally C. sativa flowers are smoked and C. indica flowers are turned into dry screen hash.
Now it is all mixed up, and most strains (actually varieties but we don't need to go into semantics) are a combination of C. indica and C. sativa genetics. Hash melt is truly a mix-n-match of different genetics. We should start a library of strain and melt quality.
Don't worry about meltyness, it is the affect on your head/body that is the true judge, and we all have unique biochemistry, so varieties affect us differently. If you want full melt, grow indica
I'm growing Jack Herer because it gives me a "happy euphoria" that I've found in only this strain, green crack, lilikoi, and strawberry cough. All three of those strains make not-fullmelt hash and give low hash yields... but the high is right. Feel me?