I feel like the riptide was really overnerfed in this eddition.
The strongest thing about it was the riptide wing. They removed formations and the riptide's ability to bundle into units. But did the nerf stop there? Not by a longshot. Even though the riptide by itself was fairly balanced in 7e, GW felt like they needed to completely pummel it to the ground. Let's look at stats, shall we?
(Stats from the online "leaks" made by GW)
Riptide base stats:
M WS BS S T W Sv (the rest doesn't really matter)
12 5+ 4+ 6 7 14 2+/5++
With the standard build, which is an ion accelerator (burst cannon is *BAD WORD DELETED!*) and 2 missile drones, the riptide costs a whopping 406 points.
Std: 72'', S7, Heavy 3, D 1, AP -3
Nova: 72'', S9, Heavy d6, D 3, AP -3
Now let's look at a similarly prices unit: The imperial knight, armed with a thermal cannon, which is very similar to the ion accelerator)
M WS BS S T W Sv
12 3+ 3+ 8 8 24 3+/5++
Point cost: 430
36'', S9, Heavy d3, D d6, AP -4
Now let's compare the stats (Imperial knight - riptide):
M WS BS S T W Sv
0 +2 +1 +2 +1 +10 -1/0
-36'', S+2, d0, 1->d6, +1 AP
Weapons (nova charge):
-36'', S0, -d3, 3->d6 (on average the same), +1 AP
What we can get from this:
-With these builds, the knight and the riptide have roughly the same number of weapons. The knight has the stubber, the reaper chainsword, the thermal cannon and the stomp (which is now a separate weapon).
-The imperial knight has some disadvantages over the riptide (armor specifically), but it more than makes up for this with his advantages (better toughness and WAY better offensive stats).
-The imperial knight has almost double the number of wounds as the riptide. Therefore, it gets to shoot for twice as long.
-The imperial knight has melee weapons, the riptide does not.
-The imperial knight gains lots of bonuses from being a super-heavy walker. The riptide does not.
-The thermal cannon is more or less at the same power level as the ion accelerator. Sure it has half the range, but it consistently shoots a high powered shot. If the riptide wants to deal, on average, 33% more damage than the imperial knight, it needs to roll for the nova charge, which is 33% chance of failure and inflicting a mortal wound on it.
The imperial knight is basically 2 riptides, with half the weaknesses and that does everything better than the riptide (including shooting at a far more consistent hitting rate) for 24 points more.