On MTGA currently there is a bug with Dragonhawk, Fate's Tempest where the ability will count previously exiled cards with a different Dragonhawk on the field than the one that created the delayed trigger. The rules text specifies "The delayed triggered ability created by Dragonhawk's last ability counts only cards that were exiled by the ability that created it. It doesn't count cards exiled by previous instances of Dragonhawk's last ability or by the abilities of other Dragonhawks you may have controlled previously."

Just completed a match where opponent had played a Dragonhawk, i killed it, then they played a second with 0 cards in library and the delayed trigger of the first killed me. The previous Dragonhawk was no longer on the field and thus could not deal damage to me with the delayed trigger. This as far as I can tell is a bug.