Originally Posted by
Effinhunter
If we're talking about ToT Finder gear levels, the tier bonuses are going to be worth way more than replacement non-tier finder gear. Way more.
If we're talking about ToT Normal gear levels, the tier bonuses, and assuming ToT LFR or Normal ranged weapon, the four piece is still going to be better than breaking it for even TF normal gear. The two piece is independent of weapon level, so there is no gear configuration that I know of (head, shoulder, chest, gloves, or legs) that would compete with that, even if it was a thunderforged upgrade. Heroic Thunderforged upgrade? That's a completely different story. I could have four piece 522 set with helm and shoulders, but FD shows a 2k dps loss if I were to take off my TF Gaze and HTF Static Shot. The set bonus is not enough to prevent you from taking most HTF upgrades in a head, shoulder, chest, hands or legs slot, regardless of weapon.
That being said, you should probably model your gear upgrades with either Femaledwarf.com or Simcraft to get an accurate answer. Almost any advice we could offer here is mired in "it depends".