The idea to fix this is simply to add more kinds of affixes as alternatives and buff existing not useful ones. Some examples:
-Currently certain items gives a slight buff to one of your skills by 5-10%, since just by adding 10% damage to a primary skill of some socketless, crit less legendary weapon is just useless. Then how about we add 100%? Now what would you think of a 800dps no socket, no crit legendary 1h weapon but adds 100% damage bonus to a random primary skill? This may also open up alternatives to some of the now overly used primary skills like FOT for monks and HA for DH (Blizzard did go in the right direction for making the Three Hundredth Spear but they just didn't go far enough). This buff can also be applied to class specific rare weapons but with it's affect diminish to 25% if the weapon rolls a socket or crit and nothing if the weapon rolled both a socket and crit.
-The above can also apply to rings and amulets so why don't we do the same thing? Buff a primary/secondary skill by 50% instead of rolling AS, crit chance or crit damage?
-How about having say a legendary glove which adds 100% bonus damage to a secondary skill but can't roll AS, crit and crit damage?
-If you think the above is not enough then whatabout armours that can boost a class of skills by 30% effectiveness? Say the device skills of DH, so we could build a DH around using evasive fire, fan of knifes, spike traps and sentry instead of the old hungering arrow and elemental arrow. Or a ring/amulet which instead of rolling just the normal affixes can actually buff 5 random skills by 20% effectiveness?
-Or give affixes that increase the effectiveness of certain runes, this would make many not very useful runes worth looking at.
-Change reflect damage to be based on enemy health or the damage they do instead of what we have now which literally does no damage to attackers. Of course to not make this OP and abusable the effect of reflect damage should be reduced on elites and bosses.
Now what about adding some debuffing affixes? Say:
-A legendary torso armour that adds 3000 life regen but -1000 LOH and -3% life steal (of course LOH and life steal bottom capped at 0)? Now people may start stacking life regen instead of looking for weapons, rings and amulets that give LOH and life steal.
-A torso armour that adds +2000 armour +150 all res but gives -10% attack speed and -5% crit chance?
-We can extend this idea to all items whereby they can generate certain affixes beyond their current cap but when it is beyond the cap a debuff affix will be generated to counter this.
-Well use your imagination, giving large bonuses to one affix well debuffing another will certainly generate much more builds and usable items.
Also class specific items (especially the helms) are currently almost indistinguishable to normal ones as the only difference is that they get a small chance to roll a class specific bonus. I think if we make them able to permanently give class specific bonuses then people may start using them more, the skill bonus will also encourage more build diversity.