So, although the triple product is an excellent metric, it would seem to me it is useful only if resolution of the down stream issues are believable
The triple product only says anything about the physics, not the engineering feasibility. It is almost certain that the first few generations of break-even and net-power machines will not be feasible as actual power plants, even in the best case scenarios.
Even for the main-stream approaches like ITER, where most of the physics and scaling is well-understood, there still remain some pretty serious 'first-wall' engineering issues which could kill the idea of an economically feasible power reactor even if net-power is achieved. Fusion at levels meaningful for power generation puts out some pretty ridiculous particle flux (even higher than a fission reactor) that tears up many materials in a fairly short time. A big problem is there simply are not many ways to test how materials will stand up in these conditions because we have no way of fully creating those conditions without a power-sized reactor.
Most of the third-party approaches like tri-alpha, field reversed configurations, polywell etc. will all have similar issues for power reactor size machines. Dense plasma focus will also have to deal with electrode erosion, though that might not be a big issue since they should be able to be made relatively cheap and easy to swap out.
The most promising thing about general fusion in my opinion is how their process might inherently solve the first wall problems due to its liquid state.