Invisible Blade is currently a class not taken so very much. On the latest release on class distribution numbers, they only reach a 1.8% despite being a class that is supposed to heavily benefit players that use a rogue playstyle. viewtopic.php?f=23&t=5956&p=339718#p339718
This is more so feedback on the class entirely rather than just throwables, but I will provide feedback on that first.
I don't really see a reason for Throwables to not count towards IB Bonuses. They are all Small or Tiny weapons, concealable due to that and, since they are all Slashing/Piercing weapon types, should realistically cause bleeding if you're struck by it. (The weapons I refer to specifically are Throwing Axes, Throwing Knives, Darts and Shuriken. Sling is an obvious exclusion since it doesn't share that weapon type.) This would open up IB's, especially Small/Tiny size players, to having a wider variety of weapons they can resort to depending on the scenario instead of only 1 weapon all the time.
You might ask, wouldn't that defeat the purpose of Crippling Throw? Yes! Yes it would. Crippling Throw is BAD. Another ability that requires you to spend a full turn just for the hope that it lands, and 99% of the time it will not because it's DC is very low. for an ability that only applies a 50% slow and 2 bleed stacks. It would be much faster to throw out a Grease/Entangle/Web from a wand/scroll because they do not require a save for the slow and take the same or less time, and throw a couple daggers (if it were possible, that is) to get a couple bleed stacks in, or run for Hide cover while they're slowed and sneak in a couple hits for those stacks.
Invisible Blade is also pretty difficult as a class to get into. Arcane Bleed is difficult to pull off without spending an entire turn doing it. It's rather inferior to purchasing a bunch of Greater Spell Breach scrolls/wands(wands found through loot matrix) for cheap and having the freedom to use those at range in the same length of time that Arcane Bleed requires from you, without the requirement to land a hit, without being in melee range and without a 3 minute timer. This ability is supposed to be something that lures you into wanting to play Invisible Blade, not make you think you could go without it if you spend a little extra coin. I feel like turning Arcane Bleed into an instant action, shared with all the other Instant Action's like Eviscerate is, would make it more appealing to have. It's the only ability in this class, out of all five levels, to be attractive along with the Bleed stacks. It should function far better than any scrolls or wands.
The class only has 5 levels for a reason, and those 5 levels should be vital when it comes to figuring it into your build, since you could instead take something like Loremaster, which gives you a HUGE array of things to choose from in only 5 levels for slightly less AB (Avoided by taking Weapon Trick, which as a Rogue, you should.) in exchange for FOUR SECRET KNOWLEDGE FEATS and 5 SCROLL AND WAND MASTERY FEATS, that give you a chance to NOT use those scrolls and wands that you're using INSTEAD of Arcane Bleed and Crippling Throw. Right now there is very little reason to pick the IB dip over something like Loremaster.