Why doesn't pve have pvp combo structure?

[Satarn]

Part of the problem is that most of the jobs that are complained about for their "press this button 5 times in 10 seconds" burst buffs those burst use the same button that is already being hit quite regularly. There is a fair amount of difference in engagement between spamming Bloodletter/Fellcleave 5 times and casting Holy Spirit 5 times when you are already hitting Bloodletter/Fellcleave every 7th or so gcd.

Erm, and that is an argument against my point... how? The combos are the bread and butter of all melee rotations so they're an even bigger part of the gcd contribution than the gauge spenders like BS or FC. Some jobs don't even have gcd spenders or other "solo gcds" to break up the combo monotony at all.

With the example of DRK, right now Bloodspiller button is pressed about 6 times per minute while each of the combo buttons is pressed a little over 6 times per minute. That means a consolidated "Souleater Combo" button would be pressed over three times as much as Bloodspiller is right now and with way shorter breaks in between. If somebody's already sick of mashing BS, they'd be far more sick of mashing this new "combo button".
Even in case of jobs with branching combos, most would still end up spamming quite a lot, just with one or two other gcd buttons to press(also 2-3 times in a row) every now and then for the buff/dot upkeep - which is not much unlike how WHM will occasionally press Dia or one of their afflatus GCDs or how SCH will use Biolysis and Ruin II.

The healer dps spell spam is more the result of problems elsewhere. A button that was intended to be hit only on occasion is being spammed constantly due to disconnects between healer design and fight design.

The intention doesn't matter in the slightest - all that's relevant is the actual result and its conclusion, which is that many people don't enjoy spending majority of the fight spamming one gcd button over and over.