You can use Composition
.
Longhand
Composition[#, Exponent[#, Variables[expr]] &] & /@ {f1, f2}
Shorthand
#@*(Exponent[#, Variables[expr]] &) & /@ {f1, f2}
Both give
{f1@*(Exponent[#1, Variables[expr]] &), f2@*(Exponent[#1, Variables[expr]] &)}
Hope this helps.