While I haven't really paid attention to the numbers in vAS, all other trials permit stam to do well. vHoF and vMoL require the most movement of the full trials and stam shines. Craglorn trials are mostly just stack and burn with a few fights requiring slight movement.
Single target stam, caltrops and endless hail with VMA bow is close but AOE magic.
Sorcerna, proud beta sorc. RIP April 2014 to May 31 2016 DArk Brotherhood. Out of retirement for negates and encases. Sorcerna will be going back into retirement to be my main crafter Fall 2018. Because an 8 k shield is f ing useless. Died because of baddies on the forum. Too much qq too little pew pew. 16 AD 2 DC. 0 EP cause they bad, CP 2300 plus 18 level 50 toons. NA, PC, Grey Host#SORCLIVESMATTER actually they don’t or they wouldn’t keep getting nerfed constantly.
Depends on trial, build, rotation and player. There's no one correct answer.
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AD High Elf Mageblade DPS (General)(Former Empress) -- Stormproof/VMOL, VHOF, VDSA completion
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With the exception of vAS ofc. Maybe a team will find a way in the future to make Stam better for that trial.
DPS-wise, Stamina beats Magicka by quite a bit. You basically run as many Stamina DPS as mechanics allow, then fill with Mag DPS (NBs, then maybe 1-2 Sorcs).