But you know what's really surprising? It was worth the cost increase.
With four slots for weapons (7 options) and/or support systems (10 options), access to the Signature Systems list (8 options) and the ability to take two drones (3 options), the Commander is far and away the most customizable unit in the codex. The number of possible configurations is absolutely staggering, and you can make a good argument for a wide range of them. Far too wide a range to cover in any kind of detail in a review like this. Instead, let's just say that the Commander basically breaks down into two general roles; providing support, and spearheading the assault.
Before getting into that, however, there is an element to the Commander's wargear that can be spoken of as a pretty universal feature. Iridium Armour (T5/2+) and the Stimulant Injector (FNP) make the Commander an absolute beast, a perfect mirror image of its old, easily dispatched self. Far from being possibly the easiest Slay the Warlord point to get, the new Commander is one of the toughest. Some also add in a shield generator (4++), but while it does increase the Commander's survivability it doesn't do so to a tremendous extent, and it is expensive and eats a Support Systems slot. Players who expect to face a lot of AP2 firepower without widely available cover will almost certainly want it, but it's not the Must Have that the Iridium/Stims combination is.
So, support and spearheading.
As a supporting model, the Commander is arguably second to none, right up there with things like the Eldar Farseer and Guard CCS. The model's extremely high defensive abilities make it very difficult to deal with at range, which is where the support Commander will likely stay. Customarily, the support Commander will be bringing along the Multi-Spectrum Sensor Suite, Command and Control Node and Puretide Engram Neurochip. By passing up its own shooting phase to use those signature systems, the Commander can make every gun in its unit count as being twin-linked (MSS), have Ignores Cover (CCN), and stand a very good chance of killing whatever vehicle or MC that unit is pointed towards (PENchip). The Commander can also take a Drone Controller, which allows all drones in its unit to use its BS5 when shooting; attached to a unit of marker drones, you suddenly have T4/4+ BS5 markerlights, which can not only move and fire, but perform the Tau's signature JSJ. As for those whose opponent's leave plenty of units in reserve, a support Commander with a pair of missile pods and the Early Warning Override can make a mess of a vehicle or MC in the opponent's phase (4 BS5 S7 shots with Tank or Monster Hunter), and then buff the rest of its unit by passing up the shooting it wouldn't get anyway. The support Commander may not bother with much in the way of weapons itself, but its presence will be felt in the corpses and wreckage left in its unit's wake.
On the other hand, the extreme durability of the up-armoured Commander means it is particularly well suited to taking on the most dangerous roles. Whether kitted out for quality (2 x plasma rifles) or quantity (AFP, flamer), or something in between, the Commander has the stats to lead an XV8 squad into the heart of danger, and out the other side. The assault commander will be well-armed, to take advantage of his high BS, but may also forego a round of shooting to use the MSS and CCN, to make absolutely certain that the unit he's leading kills whatever major threat they're aimed towards. This is especially common if you have a quantity Commander leading a unit of plasma/fusion against a quality target; not firing the AFP at a Dreadknight is not a particular loss. It's also not uncommon to find the assault Commander equipped with Vectored Retro-Thrusts (Hit and Run), the Onager Guantlet (trade all attacks for one S10 AP1) or the Neuroweb System Jammer; for a measly 2 points, the Jammer lets the Commander nominate a unit within 12", and afflict all their weapons with Gets Hot. Given how likely it is that the assault Commander is either dropping or jumping into the heart of the enemy deployment zone, there should be no shortage of rear-area support weapon units available, just the sort to afflict with this particular malady. Sadly, however, the wording of the Jammer explicitly limits it to working in that Shooting phase; it won't stick around to put a cramp in Overwatch.
The Commander can also be accompanied by a Bodyguard team, at most two battlesuits with the standard 3 slots for ranged weapons and/or support systems. Unlike the basic XV8, however, bodyguard team members can take unlimited additional support systems, rather than having them compete for one of just three slots. Given that the Elites slot has been crowded up a little by a certain Tau MC, it's not unlikely that bodyguard teams will see more use, particularly at higher points levels, where FOC crowding rather than a lack of points limits XV8 presence. On the other hand, the Tau have so many solid units now that the battlesuit isn't the absolute Must Have it once was.
The Commander is the default HQ choice for Tau players, mostly because it's a damn good unit, but also because it's the unit most established players will already have. It was mandatory in the last codex, after all, and even if it hadn't been it would've been stupid to trade it for an Ethereal. The days of unquestionable battlesuit dominance of the HQ slot are over, however. There are a variety of new infantry HQs, and while they don't have the customization, they also don't have the steep cost. We'll dig into them, next.