As a fan of Lovecraftian things the basic premise of ancient fish-people living underground, surfacing only to kidnap people for sacrifice, makes me feel that I should like kuo-toa more than I do, but as with last's weeks batch of assorted evil humanoids they--along with the rest--just come across as confusing and boring.
Let us go down the list:
- They are evil, but "only" neutral evil, which actually seems odd given that they hate discipline and are largely insane.
- They worship a naked, female, half-lobster, half-human deity. At least with drow their iconic god can look like a drow, spider, or some mix thereof.
- Their bodies are coated in a slippery substance that makes it difficult to pin them down, but they coat their shields in a sticky substance so that weapons stick to them.
- They are immune to poison and paralysis, resistant to lightning, and some can join their hands to create lightning bolts.
I like the idea of kuo-toa as an ancient race, because it helps tie them together with aboleths and/or Dagon, which is always a plus in my book. I do not think that they need to have lived on the surface, certainly not in any kind of great or advanced civilization, but I guess if you really wanted to go with them as former surface-dwellers, why not have some sort of disaster drive them underground, instead of having humans show up and take their land? Maybe they were forced underground when the sun was created/born/whatever, or the oceans receded?
As for their alignment, this is where I could see a divide. The crazy, inbred kuo-toa would be Chaotic Neutral (including some of the nobles, which gives me a kind of Charles II vibe), while the rest that follow Blibdoolpoolp would range from Neutral to Neutral Evil, depending on how they perceive her doctrine and follow through with it. This could add to social role-playing, where not all kuo-toa want to eat and sacrifice humans just because.
While I am not a fan of Blibdoolpoolp's name (while writing this I kept writing poop), I otherwise think she is actually fine as an object of crazy fishman-worship. I imagine clerics not choosing their path, but instead being born into it: they are more eel-like, with jaws filled with jagged teeth and elongated heads. They wear headdresses made of layered plates that give them a somewhat lobster-like appearance, and they can channel lightning.
Sahuagins are not as confusing, but still have their share of problems. Why are they lawful evil? Essentially as humanoid sharks I would have pegged them for neutral or even chaotic. I guess they could also be evil, but I do not see why that is necessary. Maybe some just think of everything not-sahuagin as prey?
How do they even maintain crossbows? If their jaws and claws work well enough, why do they even use weapons at all? Why are they vulnerable to fire? Is that going to be a thing that aquatic creatures have, now? Having them go into a frenzy when wounded is fine, but I preferred it in 4th Edition when they gained bonuses against wounded creatures. You know, like a shark smelling blood.
I have only used bullywugs twice: once in the first encounter of the first adventure of an Eberron campaign, pretty much because they were in the Shadow Marches and I had never used them before, and the other when I ran Stick in the Mud.
In 3rd Edition there was not much to differentiate them from other 1 HD evil humanoids. They were not hampered by marshes and mud, instead gaining a bonus to Hide checks, and I guess their clerics had a random chance to summon an extra monster?
4th Edition mixed this up by penalizing you if you used a healing surge while standing too close, and regain hit points if you critically hit one. Interesting if limited, and certainly different from other monsters, but the best additions were the various leap-attacks--especially the ones that could hurt them if they missed--and ability to belch poison gas at you.
It sounds like they are cribbing a bit from each edition, which is nice, but I would give them optional powers that let them add various poison effects to their attacks. Given that only one kind of frog seems to have claws at all, I would remove them (or make it another optional power, which could include a multiattack).
Another thing that I recall from their 4th Edition lore, which might have been in Stick in the Mud, was about how they could corrupt or warp reality when they gathered in an area for too long. I dunno, something to consider.