I don't think it's as straight forward as this.

If you're intending to hold your coins for a very long time then sure, measure in BTC. If you're scalping and moving money back to fiat then i think measuring against USD is fine as this is what you'll want as an end result: More USDs.

I get that if you're not out performing BTC then you may as well just hold BTC as you're better off but making USD gains on alts could still be a measure of success for some.