The Catachan grenade blast ability is getting a damage nerf in the 3.8 patch that`s to be released today. They are an expensive Tier 1 unit. 400 req 40 power. They are the second most expensive T1 unit behind Space marine`s ASM squad at 500 req, 50 power. I don`t know what their upkeep cost is though.
As of 3.9, Noise Marines. 400-40.
Also, Catachans hardcounter all three of those units and ASMs, while winning 1v1 melee battles against upgraded Banshees and Sluggas, and out-shooting 1v1 every ranged unit (or outmeleeing it if it doesn't).
And are detectors (counter Lictor Alpha, Kommando Kob)
And have a brutal anti-building.
Their only weak point is that if they get caught out of cover by 2 ranged units they will lose a few models, which is rather expensive to replace, and they have slightly heavier reinforcement costs than other T1.5 units because they will usually lose a model or two every engagement.
ASMs rarely lose models, Ravenors can kill ranged units with devourers without losing models which pushes their cost to 460-70, Stormboyz lose models a lot, but they do so much damage they will kill more, Rangers pick off models one at a time and can just retreat if they are jumped without losing anything. Noisemarines are overpriced right now, but they are just as resilient as CSMs.