If you plan to run fire blast, which was a scenario in which you described stall(or balance using the best special wall in the game) putting more pressure on excadrill, you pretty much have to use blissey, who can't switch into many threatening special attacks, like specs kyogre hydro pump, the 2hko from a nped darkrai, and many, many others. More importantly you lose the ability to come into and out heal many physical attackers, like support groudon, and can no longer take stuff like Latios psyshocks and heal up. Blissey is clearly inferior to chansey, as stall can't viably check many threats (remember gen 4 specs palkia?) without it. I don't see how you. can claim stall's viability isn't in question, when it is a hazard based playstyle, and nearly all of the "best" walls allow excadrill in to threaten the team, even more so now that it can do its job burned. Forry is also one of the most common and best pokemon present on stall teams. But I agree that it doesn't just affect stall as a playstyle.
Considering that balanced teams will be running similar walls to stall in most cases, they will be similarly affected. Granted they will probably have at least two members who put excadrill or other OHKO users under more pressure, but they are more vulernable in two sense. One, they often have no room for secondary checks to threatening pokemon like Sheer cold Kyogre or Excadrill. Two, they are often just as dependent on hazards to allow their often specialized sweepers to punch through teams.
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