Most people who enter RvB arrive with little or no PVP experience, and are intimidated by the prospect of joining a fleet with almost no basic knowledge. Others come from a low or null-sec background with a bias toward strict fleet doctrines and scheduled CTAs.
Neither know off the bat which ships 'work' for a successful RvB career. You can certainly fly your HAC or T3 BC around and find things to kill. Flying something more expensive than a T1 Cruiser typically attracts a lot of undesired attention, though, and with the enemy HQ no more than two jumps away, your Cynabal may quickly be taken out by a fleet whose collective ISK value is less than half of your hull.
In fleets, your first task is to be useful. If you can apply DPS and web a target, you are already useful. If an enemy FC knows that you're going to be particularly damaging and not too hard to kill (Catalysts, for instance), you will be primaried quickly. If your hull is worth more than your surrounding fleet combined, you will be primaried quickly. In other words, if you try to stand out from the rest of your fleet, though your sacrifice is appreciated, it will get you no further on your killboard than if you'd flown a T1 frigate.
FCs can count on some targets being soft and others being hard. Mallers are typically the last cruiser to be primaried in a fleet because they easily reach 50k EHP yet don't output a tremendous amount of DPS. T1 frigates will be primaried sooner than Mallers, even after the latest Tiercide buff which gives Mallers over 300 DPS plus that 50k EHP tank. They are easily the most useful Cruiser to bring in a fleet if only because they will stay on the field longest of the T1 Cruisers (and thus lay down more damage and points/webs on more targets). A Thorax might put out twice as much DPS, but it won't stay on the field for even half as long.
This is a modern (Post-Retribution) Maller fit. Before Retribution, Mallers were commonly fit with 200mm Autocannons and two 1600mm plates for massive tank. While it's possible now to fit medium guns and two plates, this would require the use of ACR rigs, which effectively adds 10 million to the pricetag on your cruiser. While you can expect that your Maller won't be primaried on the spot, you should be ready to lose them. For tracking frigates - the backbone of most RvB fleets - 200mm Autocannon fits are still popular, but medium lasers easily track scrammed and webbed frigates.
But beyond this, the Maller is surprisingly versatile. Aside from the almost mandatory bits (a plate for buffer, damage control, hardeners, guns of some variety, an afterburner) the rest is up to imagination. Two webs are great for catching AB frigates. Tracking disruptors and sensor dampeners also help by reducing the effectiveness of large targets or forcing Logistics cruisers (the T1 varieties have seen widespread use in RvB since Retribution) to move in closer to the action. Some folks choose to fit their Maller specifically for DPS, since they can usually expect to not be primaried until late in the fight. I've seen blaster Mallers lately that can put out over 500 DPS (albeit with much less range than a similar laser fit) while keeping the 50k EHP tank.
A Maller can be fit on the cheap for around 20 million ISK, but if you have fitting implants and some ISK to blow, why not go for broke? T2 1600mm plates add a nice chunk of EHP. T2 guns enable you to use Scorch crystals, which effectively extends your range beyond 20km. Active tanking is possible, though you shouldn't expect Myrmidon-like performance due to having only three mid slots. The only thing a Maller can't be expected to do is move quickly; even without plates, it's still one of the slowest T1 Cruisers.
Next time, I'll discuss undock tactics and baiting.