Taking a look at poison, snipers, and gargantuan MCs.

[Charon]

Maybe not, but then again you KNOW there is a problem with your Codex when you have one trick ponies and they don´t do that trick very well or at all.

Just look at the weapons...
You basically have only 2 weapons in the whole book. Lance and Poison.

[Archon Charybdis]

As for Talos and Grotesques i would say what are they even doing fighting normal troops? before hand these where the guys you threw against the elite the Terminators, Dreadnoughts etc etc.

Grotesques are pretty good at killing Termies provided they don't have some way of getting S10 (which admittedly is rare), but you know what else a colossal volume of S5 poison attacks is good for killing? Pretty much anything that's not a vehicle, which includes hordes of cheap crap and semi-elite units like SM or other Eldar. There's very few bad targets to point Grotesques at.

The Talos isn't a great choice against either Termies or Dreadnoughts though, and I wouldn't necessarily expect it to be at it's fairly low points cost. It's got a good WS to make the most of it's modest number of Attacks, and S just high enough to wound semi-elite infantry like Marines on 2's. It's pretty much tailored specifically for killing units of power armored guys and it really only needs to take care of one squad to earn it's points back.

[Charon]

Grotesques are pretty good at killing Termies provided they don't have some way of getting S10 (which admittedly is rare), but you know what else a colossal volume of S5 poison attacks is good for killing? Pretty much anything that's not a vehicle, which includes hordes of cheap crap and semi-elite units like SM or other Eldar. There's very few bad targets to point Grotesques at.

Grots have no "colossal volume" of poison attacks vs terminators. The majority comes from their Rampage rule which requires them to be outnumbered. Not gonna happen with termintors which come most often in squads of 5.
That means an amazing number of 20 attacks (if you are the one assaulting from your raider and you will need an IC as Ld3 is dangerous) which results in 1,5 dead terminators. A Ravager for mere 110 points is more effective.

The Talos isn't a great choice against either Termies or Dreadnoughts though, and I wouldn't necessarily expect it to be at it's fairly low points cost.

The fairly low points cost is 25 point higher than a dread for less attacks, less S and a lower BS.

[Archon Charybdis]

Grots have no "colossal volume" of poison attacks vs terminators. The majority comes from their Rampage rule which requires them to be outnumbered. Not gonna happen with termintors which come most often in squads of 5.
That means an amazing number of 20 attacks (if you are the one assaulting from your raider and you will need an IC as Ld3 is dangerous) which results in 1,5 dead terminators. A Ravager for mere 110 points is more effective.

4 Attacks stock with 5 on the charge is a colossal number of attacks, especially when comparable points to a 5 man TH/SS squad gets you 6 guys (with one extra from the Abberation). That's 25/31 Attacks, even without Rampage. Ld3 is only an issue if you're not running a Coven list to make them Fearless (in which case you really should be). But even if you include a Haemonculus--a comparable points worth of Grotesque/Haemy unit will still have enough attacks to likely kill 2 terminators, take maybe two wounds on a Grotesque in return, and then kill them over the course of another few rounds. Even if the termies get the charge, the Grots will still win out eventually.

The fairly low points cost is 25 point higher than a dread for less attacks, less S and a lower BS.

I think that's more of a statement on how GW wasn't selling enough Dread models than the Talos being bad. Also it's the same attacks with a better WS, unless you're taking a variant with two DCCWs. The Talos' gun is also TL-ed which makes it more accurate than the Dread's stock. There's also the significant advantage of having FNP and being an MC which means easy cover saves, all of which can make it quite a lot more durable against shooting.