Here we are, our new codex, and many new models, released. Now, it's up to us to figure out how to use them. Where better to start than the heretofore uncharted territory of the Riptide?
To begin with the obvious, it is extremely durable, being tougher than dreadknights, with the ability to overcharge it's shields and take drones who share it's toughness value. It is also as mobile as a crisis suit, while toting guns that make hammerheads blush. Being a monstrous creature also means that while it is not great in CC, it can still smash tanks and well armoured shooty units (i.e. devastators).
But how to optimize it's use? There are three key points, really:
A good start would be to make sure it's main gun and secondary gun synergize well. A tank-melting secondary paired with an infantry shredding primary would not, for example, have that synergy.
Furthermore, it is tough, but not indestructible. Keep it away from things like Grey knights, librarians and any other creative ways your opponents can think of to take away all it's wounds at once.
Finally, remember which army it is a part of: it is not designed for lone-wolf combat, diving into the thick of it and turning the battle on it's own. It is designed to be excellent in both giving support, and receiving support.
As for it's guns, we have a lot to think about.
Heavy Burst Cannon
-High Shot count
-Effective against flyers with a velocity tracker
-Gains rending and an even higher shot count when nova charged
-The Riptide has mediocre Ballistic Skill, and you will REALLY feel it while using this particular weapon
-High shot count, Gets Hot! and nova charging all add up to a lot of self-inflicted pain
-Not especially useful against heavy vehicle/infantry/monsters
-Mediocre even against hordes, which it is supposed to be really, really good against
Overall the Heavy Burst Cannon isn't terrible, but paying the points for a riptide to score a handful of medium strength, poor AP hits a turn from closer than it is usually advisable to be? Requires playtesting, but I don't think I'll ever feel the need to use it.
-Can penetrate terminator armour
-Can fire blasts equivalent to battlecannons, except these also have enough AP to beat terminators
-Can Nova Charge to fire blasts that would feel at home amongst IG artillery.
-Great for monster hunting
-Lower shot count than the Heavy Burst Cannon
-Gets Hot! on blast weapons can really screw you over
-Less effecting against most aircraft than the Heavy Burst Cannon
The Ion Accelerator seems to be, overall, a better choice than the Heavy Burst Cannon, except against aircraft, though the Heavy Burst Cannon is a bit less random, being able to roll a Gets Hot!, fail, and still get some shots off.
Now, let's look at what has synergies with what. The Riptide's secondary weapon options are TLPR, TLFB and TLSMS. The SMS work best with the Heavy Burst Cannon, and the plasma rifle works decently with it. Avoid FB+HBC though, as their roles are a bit TOO different. The Ion Accelerator, on the other hand, works exceptionally well with FB, as well as with PR, for anti-tank boosting and anti-monster/TEQ busting, respectively. The SMS could work somewhat decently with it if you intend to use it to clear out mass cover-camping light infantry, but if that is the case then you should probably be relying on more appropriately equipped units for your anti-GEQ.
TL:DR, the XV104 Riptide can be used in a variety of roles, with different configs being suited to different tasks. Make sure you keep your monsters supported, so that they can continue to support you.