The only situation where a Reaper aka the most deployed Magitek Armor was one shooted by magic was on the End of an Era cinematic (where everything uses the rule of cool) and was done by the BLM companion of the Wol, someone not in the level of "veteran mage" but on the prodigy scale and looked like a lucky shot. Reapers are stated to be strong enough to fight with against entire squad alone and win. True, Magitek run out of fuel/ammo, but same can be said of normal soldiers running out of magic power and endurance, unless the supply lines are completely cut its a non factor.

Eorzean Alliance got better at fighting Magitek but that doesnt mean they are easy picking. They are facing with mostly infantery the fantasy equivalent of tanks and despite the pilot being quite exposed doesnt seem a too big of an issue considering they didnt altered its design yet

Canonically Elidibus was stated to be stronger than the Zenos we fought (current Zenos post "resurrection" is hinted to be even stronger though), he simply compensated his worse swordmanship with ascian magic. The fact that Hien Yugiri and Lyse werent instakilled and managed to survive until the Wol arrived speaks about their much above than average power, considering that Yugiri and Wol in the second fight were only able to put a nominal fight until Zenos got half way serious and quickly defeated both once he pulled out Ame no Habakiri.

Yoshida himself stated that power level, and until now is the "canon" even if not updated of the comparative power of the Wol (and by extension you can extrapolate to the rest of the setting)