I think that only +1 to DC is meaningless, but +1 to DC *and* to caster level is too much. I understand your point of view but it is not feasible. Most damaging spells could benefit from both increases, that in many cases translate in +1 DC and +1 damage die. A first level standard sorcerer with SF (Evocation) + GSF (Evocation) could cast four 3d4 burning hands with a save DC of 15... greatly better than four 1d4 burning hands with a DC of 17 (with 3.0 SF + GSF).
A hypotesis for the new Spell Focus could be:
+1 to DC if the spell grants a save
+1 to caster level otherwise
(there is a sort of a precedent with the fire/cold subtype: -10 to the save if the spell grants a save, double damage otherwise, if I'm not wrong)