Tackling the drain of a spell with blood magic or summoning a blood spirit actually do very little to hasten the arrival of Horrors. The ritual used by Daniel Coleman to perform the Ghost Dance, or whatever the blood mages did with the artifact called the Locus, really were significant events. After Harlequin and Dunkelzahn disrupted Darke plans, blood magic is more of a long-term threat (at least until yet another sinister plan is discovered).
Back in 2056, at the time of the Aztlan Sourcebook, the major Awakened players knew the Aztlaner practiced blood magic, but do not worry too much about it. They are still baffled to learn that the blood mages of Aztlan may know the real implication of they're doing. Only Dunkelzahn is slightly more knowledgeable, but he devoted a lot of time and resources to spy on Aztechnology, while having a seat on their board of directors. Dunkelzahn also suggests that Hualpa and other Amazonian dragons are well aware of Aztlan use of blood magic, but chose to stay silent about it, withholding information even from other Amazonian awakened (rather than recognizing that the knowledge of blood magic the feathered serpents taught to metahumanity to fight off the Horror during the Fourth World wasn't lost as they thought it would).
In 2057, Dunkelzahn put an halt to the early coming of Horrors. Darke is either dead or on the run. By 2061, the evil force behind Aztechnology maintained its hold on the board members, the remaining blood mages were only a small number of rather high-level Initiate (grade 8+) hiding from internal purge or deported.
At this point it would have made sense for dragons to consider Aztlan blood mages were no longer a major threat, because that was what SR authors wanted it to be! It was the Apep Consortium who was supposed to be the new front for Horrors.
But the blood mages of Aztlan have returned since, first during the Yucatan War, then at the highest level. The recent sourcebooks suggest blood mages are now again considered as an elite inside Aztechnology and Aztlan. During the Colombian War, one of the most secret unit of the Aztlan army was the Blood Daggers, with 30-40 blood mages, receiving their order directly from HQ, with a focus on eliminating Amazonian high-level initiates.
I can see the immortal elves from Tir Tairngire being more occupied by their own situation, Lofwyr wary that taking on Aztechnology would be interpreted as a move from Saeder-Krupp CEO and have geo-economical consequences. Ghostwalker would be the most willing to take on Aztechnology. Maybe he considered regenerating Zebulon/Yuichotol was his priority.
It's possible the great dragons actually consider the knowledge of blood magic by metahumanity in America is the concern of the feathered serpents who taught them in the first place, ie. Amazonia. Though it technically was triggered by Aztechnology, the Colombian War may actually be the first part of Hualpa and Sirrurg action to deal with the threat of blood magic.
It would shed a new light on Hestaby condemnation of Sirrurg war crimes. If other dragons said it was up to Hualpa, Sirrurg and their allies were to use any mean necessary to eliminate the Aztlan blood mages (a sort of Council Mandate), without setting any limit, it would be difficult to condemn Sirrurg action afterwards. That would explain why Hestaby didn't call a draconic meeting to discuss Sirrurg action first, and moved it to the UN instead.