Channeling is a good reason to have them blocked. If this shield effect goes off vs archer shot then thats just great. The shield needs to be left as a tool for dexers. If the distance damagers have an issue I hope a blocked spell can also give the para effect also.
Well I am pro for spell channeling. Archers win by a repetitive ratio from a distance with a variety of special moves with the addition of a slew of item properties to curb the situation in their favor all the time.
Mages however lack the killing power versus an archer in the same time frame. A mage usually needs to get the initial first attack. A 2 spell combo, followed by a 3rd and usually needs a 4th to finish off, but in most cases the target pings off. Each time a mage cast he/she is frozen in place, while archers can shoot and move at the same time with much more damage to boot.
All said most mages now a days are put in a defensive mode unless they fight in groups.
To get the full benefit of Parry one needs 80 dex, a heavy investment for any mage. Also the para effect most likely can be broken by a trap box which something most archers/dexers are quite skilled at these days. I see that a spell channeling boura tail shield would be an equalizer and make it so that mages are not just roving arrow butts.