I feel as though the nuke wall and BP wall is an issue of abusing a specific advantage and stacking it. I would feel very comfortable if there was a nuke wall and bloodpact wall only if the sources were coming from different players of the same job.
For example, 3 blm death bursting would receive a penalty on 2/3 blm, but a geo, a sch, and a blm all bursting would receive no penalty. This would open up using other jobs in ways originally intended and go with the flow of odyssea where multiple jobs are required. Geo nuking and sch nuking would become relevant again. A single smn using apogee or conduit would be useful again.
It would make each job feel more of their own and promote better combinations and less abusing an advantage.
I would also love to see a similar this taken towards weaponskills. If one person is spamming savage blade there's no penalty. If the entire party is spamming savage blade then a weaponskill wall is implemented to deter mindless savage blade spamming and have players consider using more then one weaponskill.