Are any other alternative voting methods better at solving the “spoiler problem” than IRV?
No. IRV is just about the best solution to “spoiler” problems. Some advocates of other reforms, such as Range or Approval Voting claim that IRV does not solve the spoiler problem in all situations — specifically when the “spoiler” can out-poll one of the major party candidates. Note that this is incorrect as this situation does not meet the usual definition of a “spoiler,” and is instead an example of the little-known “center-squeeze” dynamic common to all runoff methods. It is important to note that these alternative methods suffer from their own version of the “spoiler problem.” Approval voting is probably less prone to spoilers than plurality elections, but is not immune. A key fact to understand is that whether a voter “approves” (votes for) a particular candidate depends on what other candidates the voter has to compare the candidate to. Here is a spoiler scenario under Approval: If the voter thinks candidate A is okay, and B is horrible in a two way race, the voter will likely a
