User blog comment:B214/Shin DxD 1 discussion/@comment-93.132.65.47-20180926201139/@comment-108.7.146.103-20180927000353

Ddraig and Albion are limited by being within the Sacred Gear (The ability to manifest along side Issei was not yet shown during the Vali vs Crom fight), and while Albion's Poison and Ddraig's Purgatory Flames may work, I doubt that in their original forms they would be strong enough because physically Crom is said to surpass them in their original primes. The hosts in Vali's gear are suppressed by him, and the souls of Issei's sacrificed themselves to save him from Samael's curse. Regardless their experience as humans is more limited than that of a pure dragon who had remained up and about constantly, rather than stuck as a soul in various hosts of various ability.

HOWEVER, as caveat, they have experienced and absorbed the power of Ophis, (and in Ddraig's case the flesh/power of Great Red), so we have yet to see how powerful they are now.