Yep, TF is one of the biggest reasons Thumpers can apply pressure. Basically, they make up for only having 12 Weapon Attribute over time by having that weapon flying 33% faster over a long period of time. A Beastmaster Thumper, perhaps the most common), has an 11 second /10r that costs 6e under expertise. In 11 seconds, the ranger has regened 11 energy, and can use a zealous hammer to enjoy the benefits. A hammer under IAS hits about every second; if they all hit, it's like having the net equivalent of two pips (minus the one taken by zealous mod) of regen.
Expertise is the other reason. It allows the Thumper to spam both stances and energy attacks with its two natural pips ( -zealous) and its additional two virtual pips ( +zealous).
Beastmaster Thumpers have pet attacks to complement the range of the hammer. Brutal strike is good for sealing the deal, dealing extra damage when the target is below 50% health. Disrupting Lunge is a spammable pet interrupt that refreshes every 8 seconds. Also, they have the extra autoattack damage from a pet. At 14 BM, the normal attack damage from a pet is significant, if not overwhelming. Combined with a consta-stanced turbo hammer, the Thumper can dish out quite a bit of damage.
(compare to this frenzy, which is a window that must be kept closed much of the time; the most important use of frenzy is in spiking, where the spike skills must follow each other rapidly)
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