Hold on. Hooold on.
You pulled Lich Bane into the "okay" camp when is a burst tool. To make the most out of it you need to build AP, and that's most likely a glassy build.
Triforce, which incentivises a more consistent trading pattern, in part due to its stat spread, can be built on literally anyone. A lot of folks shy away from it for a variety of reasons. Mainly the fact that it provides mana, but also because Orianna will get less use out of it than Illaoi.
Duskblade is literally free damage, yes. It depends on levels so it's more viable on solo laners, but it provides the same amount of damage regardless of who you pick.
I used to build it on Kled for example. His ganks were disgusting as a result.
It doesn't matter how much you hit the Spellblade items as long as their Spellblade proc exists.
As long as it provides an additional effect, whether it's just extra damage, or a slow, or whatever else you come up with...
By the very nature of its passive, people with autoattack resets or reliable/spammable skills that apply on-hit-effects, will find A LOT more value from them than others, just due to the to the synergy in their kits with the item effects.
Lich Bane is a little different in that it's AP-heavy focused. Its user base is a bit more limited: to people who build AP, and have a skill that applies on-hit-effects, or autoattack anyway as a part of their natural play style.
Spellblade items amplify a champion's strengths, but DFG was removed, like the other poster pointed out, because it just added so much regardless of who you hit.
- % Max HP damage on a targetted effect
- Amplifies ALL magic damage the target takes; not just from the user, but everyone else as well. (Primary users were mages so they were the magical damage dealers affected most by it, but you cannot entirely discount others' damage.)
It was a horrifically powerful active, that was literally a guaranteed, on-demand multiplier to the user's damage against a target. You could keep it on cooldown just to threaten, like a Blitzcrank holds his hook.
At much as I hate the Duskblade myself, at least it has gating mechanisms.
- Applies flat damage based on your level
- Applies only on an autoattack
- Negated if you have vision of them for 5+ seconds prior
assholes running around with it, dealing an absolute shit-ton of damage with absolutely no compensation nerfs.
and 
are unhealthy items that require Riot to balance champions around them, instead of being items that get balanced around them. Deathfire Grasp had this exact problem with AP assassins, and it got taken out because of it!
are decent because they scale with AP and enhance a specific play-style. 