Most of the time the bases have the same attack speed. Phaseblade is the one item which gets an insane boost to attackspeed compared to crystal sword and dimensional blade, but as far as I remember there are other items that get a slight attackspeed increase, and a few even a decrease ( I just looked up the numbers for the ribcracker base, and you are right on that one ).
Repeating crossbow has a lower attack speed than it’s elite and exceptional version, which are both the same, for example.
Looking up every weapon individually is the only way.
You CAN reach the same overall attackspeed with crystal sword/ dimensional blade as with phaseblade, but you would probably need tons of bonus as on your equip. You would need less dexterity to use it, but it’s still never worth it in my opinion.
Example: If you want to use grief on a smiter, you need 152 total attackspeed to reach the max breakpoint on a dimensional blade/ crystal sword. So a 40 ias grief + 112 on your equip. If you use a phaseblade instead, it’s only 54 attackspeed, so a 40 ias grief + 14 ias on your equip. That’s how big the gap is.
However, if you use a lvl 20 fanatism aura, you only need 44 total attackspeed for max breakpoints, which means you can go with a 30 ias grief and some 15 ias item/jewel.
For a WW barbarian is barely makes any difference attackspeed-wise. 34 ias will give you your highest breakpoint (just like with a berserker axe). With phaseblades 4 ias is enough (which is irrelevant, since grief gives you at least 30 ias per weapon).
Edit: A berserk barb needs 75 ias for max breakpoint with a phaseblade, but 125 ias with dimensional blade/ crystal sword/ berserker axe