Tier of mods using recombinators

One thing I can't seem to find clarification on anywhere is whether the tier of mods matters when using a recombinator? Or does it just randomly re-roll that mod irrespective of what tier it was on the original item?

While it's not explicitly stated that the modifier tiers are kept, they are (in most cases). If you have T1 cold res on one item and T3 fire res on another and you recomb them, they will stay T1 and T3 assuming you got them both on the resulting item.

The only exception to this is the chance to randomly get other effects. These include adding a new mod, divining one or more of the mods, or changing the tiers of some of the mods (though I'm not sure if this is random, or can only be up or down 1 tier).

tl:dr Recombinators keep your original modifier tier and roll, except in some cases where the tier can be shifted.