A battlesuit SHOULD be a threat to Space Marines, not just from the ridiculous firepower (which we have in these rules) but from the fact they are difficult to kill.
On the TT, an average Space Marine can kill a Crisis suit with only his boltgun and combat knife and it isn't even that super-duper hard to do (you need some 18 boltgun shots/melee strikes). Stealth suits drop even easier and Broadsides are only better armored than the Crisis suits. These suits are pretty much glorified power armors rather than pseudo-walkers like the Dreadknight.
Now, on the other hand, Hazard and Riptide suits are a much different deal. They are much more durable than the other three suits (especially the Riptide) and not just because they have more armor. For anything, I think only the Hazard and the Riptide are problematic in this supplement. They both should confer Unnatural Toughness or have some sort of special rule that would allow them to soak up damage with impunity.
18 bolter shots? That seems to imply it takes a while!
Let's assume that these are simply shots, rather than hits, and that our BS 50 DW marine is therefore only hitting with half of them. That's 9 bolter shots, each doing an average of, in DW, about 16 pen 4 damage. That's a lot of damage to kill one suit!
Now let's apply these 9 bolter shots to our friendly Crisis Battlesuit from this supplement. Let's assume our brave pilot rolled maximum toughness and got every toughness and sound constitution advance up to Rank 4/5 to make him as durable as possible. Let's also assume he's got a shield generator, cancelling a further 40% of the incoming shots. So he's got T 55 and 15 Wounds.
5.4 of the bolt shots make it through the shielding - let's round that down to an even 5. Each one must now contend with the vicious 10AP of the Crisis battlesuit. Which it punches through with ease. Each shot now deals 5 damage. 5 shots have gotten through. 25 damage to 15 wound character, down to -10. Given that this is explosive damage, he probably could've easily died one shot earlier.
And this is the toughest Crisis Battlesuit Pilot I could make. A more reasonably built one would require even fewer shots to be killed. And as soon as actual anti-armour was brought into play, he'd be completely ******.
This problem only scales when you look at Riptides and the like. These things are meant to be able to stand up to Carnifices. Can they? **** no.
Also the Heavy Railgun barely scratches a Leman Russ's paintjob. Lelwut? What happened to the good ol' MoX stat of 3d10+30I Pen 15?