I took some time to get the stats of similar sorts of small warengines for comparison. Nothing provides an exact comparison between lists, but this should at least show the sort of ball park these units are in and what their peers look like.
As you will see, most are considerably more capable in combat (all 4 versions of knights), or better at long range firepower (especially Castellans), similar resilience (through Knight SHields, reinforced armour or through void shields) or fearless (common in warhounds and up).
The fearless aspect is a big missing link, and why the way riptides tend to die is by getting hacked down or shot while broken -that's entirely on purpose and similar to their performance in 40K.
[] XV104 Riptide War Engine 25cm 3+ 5+ 4+ (Support Formation)
Ion Accelerator 45cm MW3+
2x Heavy Burst Cannon 30cm AP4+/AT5+
Tau Deflector field. Walker. Damage Capacity 2. Thick Rear Armour. Tau Jet Packs
Critical Hit: The Experimental Nova Reactor overloads, destroying the Riptide and doing a hit to any unit within 5cm on a 6+.
Compare to
[] Knights Errant (Core formation) 300pts
WE 25cm 5+ Reinforced 4+ 5+
Thermal Cannon 30cm MW4+ , FwA
and (15cm) Small Arms , Macroweapon
Power Gauntlet (bc) Assault Weapons , EA(+1) Titan Killer
Shock Lance (15cm) Small Arms , EA(+1) First Strike
Damage Capacity 2, Reinforced Armour, Knight Shield (4+ save vs macro, lance, titan) Walker Critical Hit Effect: Destroyed
[] Knight Paladin (Core formation) 300pts
WE 25cm Reinforced 5+ 4+ 5+
Battle Cannon 75cm AP4+/AT4+
Chainsword (bc) Assault Weapons, EA(+1), Macroweapon
Shock Lance (15cm) Small Arms , EA(+1) , First Strike
Damage Capacity 2, Knight Shield, Reinforced Armour, Walker, Critical Hit
Effect: Destroyed.
[] Knight Lancers (Support formation) 300pts
WE 30cm 5+ 5+ 5+
Battle Cannon 75cm AP4+/AT4+
Power Lance (15cm) Small Arms, EA(+1), First Strike, Macroweapon
Damage Capacity 2, Knight Shield, Reinforced Armour, Scout, Walker.
Critical Hit Effect: Destroyed.
[] Knight Castellan (Support Formation) 375pts
WE 20cm Reinforced 4+ 5+ 4+
Knight Quake Cannon 90cm Macroweapon W3+
or 90cm 2BP
Multi-barrelled Autocannon 45cm 3× AP5+/AT6+
Damage Capacity 2, Knight Shield, Reinforced Armour, Walker.
Critical Hit Effect: Destroyed
[] Warhound Class Titan 275
WE 30cm 5+ 4+ 4+
Vulcan Megabolter 45cm 4× AP3+/AT5+
Plasma Blastgun 45cm 2× Macroweapon 2+ Slw
Damage Capacity 3 Fearless Reinforced Armour 2 Void Shields Walker
[] Warhound Class Titan Adeptus Mechanicus 300
WE 30cm 5+ 4+ 4+
Turbo-Laser Destructor 60cm 4× AP5+/AT3+
Plasma Blastgun 45cm 2× Macroweapon 2+ Slw
Damage Capacity 3 Fearless Reinforced Armour 2 Void Shields Walker
Here are a few quotes from this thread from people who've used them, just to add a contrasting opinion.
Borka wrote:
Riptides:
I really liked theses guys. I pushed them up the field in all games. This was very nice as they're described to be spearheading attacks in the book. They felt durable enough so that I dared to do that even without reinforced and even when being my BTS. I think the change to no reinforced was good. I feel 3 saves should be avoided. Their attacks are good, but not over the top in any way. They didn't feel over or underpriced to me.
Dobbsy wrote:
Matt, what's the role/function of the Riptide? It seems fairly underwhelming as a unit type. Just two weapons and a 2DC WE with a Deflector Shield....
Borka wrote:
Riptides didn't really get to do a lot, died or failed me when they had the chance. They were a bit meh this time around. Still like them though and it's a nice change to have the Shas'O in such a durable suit compared to the crisis.
However, even after posting the above and showing the comparisons I think they are due a price bump. (I also think Knight Castellan's are due a bump, or much better yet a decrease from 90cm range on macro, but that's outside my remit
) It won't be in the region of what I Beefcake's suggesting, but a bit of an increase to make lists that try to max them out bleed for it in other areas.
I hope that explanation is helpful.