This thread will compare the Tau Hammerhead to some of Epic's other common tanks in an attempt to find out if they genuinly are under-performers, what areas they under-perform in, whether that actually matters and if so what could be done to fix them.
But first a quick recap of a conversation that's been going since at least 2010:
Matt-Shadowlord wrote:
Apologist wrote:
Sounds great, Matt-Shadowlord

Rumours have the [40K Tau Codex] suit railgun being reduced to S8, AP2; I wonder whether this could translate to the Hammerhead Railgun (apparently retitled the 'Railcannon') being upgraded to being AT3+, as it would no longer be restricted by the usual Epic conventions of being related to the twin-linked Railguns on the Broadside?
I've seen quite a few notes that the Hammerheads aren't performing quite as well as players would like, so this might be an opportunity to upgrade them. A formation of six with this upgrade would be more closely comparable to the Leman Russ tanks, which are the obvious comparison – the HH having worse AP and no reinforced armour, but being faster, ignoring terrain and having a deeper AT bite.
The issue with players reporting that Hammerheads under-performing goes back years, and it's one of the things I am least satisfied with in the Vior'la list. The problem there is that I don't want to improve them above the 3rd Phase Tau list they are based on because the goal is to provide a list that is 'different' rather than 'better' and improving such an important unit would definitely go against that concept.
What I am considering doing is creating a detailed analysis of the broadside vs its peers to see if there is actually a genuine problem or just a perception issue. If it's genuine I would be willing to slow down the process of getting Vior'la approved in order to use it as a test-case for an adjusted statline, with the idea being to see of Yme-Loc is willing to eventually consider incorporating it in the main list as well if it should be successful.
To reference your specific example, the Leman Russ is the ultimate generalist tank, survivable and good against vehicles and infantry alike, while also being extremely good in firefights (RA, 4+, Commissar, outnumber). The Hammerhead is supposedly a dedicated Vehicle killer, based on one of 40K's ultimate tank-killing tanks.
Despite that, it takes an average of 8 shots from Hammerhead Railguns to kill a Leman Russ, and 4 shots from Leman Russ Battlecannons to kill a Hammerhead.
So step 1, is there a problem with this tank in its role as a dedicated tank hunter. I will compare it to two other tanks; the ubiquitous Leman Russ as a generalist, and the Eldar Fire Prism as another Xeno tank that is about the closest thing I could find to a Skimmer with a similar role to the Broadside.
Key:
[] The table below shows the chances for a Tau Hammerhead to hit and to kill targets with three common types of armour: 4+, 4+ RA and 5+
[] The Railgun column shows the numbers for the primary weapon, the Seeker missile column shows the numbers for the secondary weapon (in this case, it can only fire of the target is markerlit). The third column 'Shots needed per kill' combines the two figures and says how many shots would be needed to kill the target on average.
[] EG To hit (standard) is the basic to hit roll without modification. To hit if Sustain is the roll needed to hit with a +1 bonus for sustaining.
[] The Tau Hammerhead table has an extra pair of rows showing the stats for to hit and to kill if the target is markerlit. This requires a model with the markerlight rule to be within 30cm and LOF of the target.
[] The Hammerhead's secondary weapon (seeker missile) cannot fire unless the target is markerlit.
The Leman Russ(note: about 62.5pts per tank, strategy rating 2, formation comes with commissar)

The antitank ability of the Hammerhead is not significantly better than the Leman Russ:
[] They both hit on 4+ with a 75cm maingun. The Hammerhead adds 1 to its to hit roll and a secondary 5+ shot if the target is markerlit.
[] The Leman Russ adds a secondary 5+ shot if the target is within 45cm, without any external requirements.
The result is a small advantage to the HH, provided it can manage to keep a markerlight unit close to targets.
The Fire Prism(note: 65pts per tank, SR4 or 5 (so likely to go first), 5+ armour but unusually survivable movement-rules)

The numbers look overwhelmingly in favour of the Fireprism at all times and all movement speeds, but especially when it comes to dealing with Reinforced Armour.
Here is a direct comparison of the Hammerhead to the Fire PrismThe below is a simplified table that just compares how many shooting tanks are required to kill each type of target.

Looking at how the tanks perform against Reinforced Armour (ie the middle column with a grey header)
[] With no modifiers if takes 8 Hammerheads to do the same damage as 2.4 Fireprisms. Fireprisms do 3.33 times more damage to RA than Hammerhead
[] A Fireprism that double moves and shoots does more damage to RA than a Hammerhead that sustains fire.
[] A Fireprism that double moves and shoots does more damage to RA than a Broadside that sustains fire on a target that is MarkerlitA Fireprism doing its most inaccurate shot while double moving does more damage to Reinforced Armour targets than a Hammerhead that has the perfect firing solution on Sustain and has a second formation at risk within 30cm of the target.
And that is why players so often report that Hammerheads under-perform, despite their being the superior Landraider/Leman Russ killer in 40K. It turns out it's not just all in their heads

Fortunately I now have all the formulas in Excel so it's easy to work out and compare the impact of proposed solutions and alternatives.