Grim Dawn: Improv Shieldbreaker Comprehensive Rework

Can you show an example of an end game build that would be improved by adding a secondary damage type (with gear and devotions included)? Cause I'm seeing a lot of builds on facebook, reddit and forums of people focusing on one damage type only and doing all celestials bosses as well as 75-76 shattered realms and crucible gladiator at record speeds. And again, why do endgame sets seem to convert into a single type if dual type is the best way to go? Seems odd to be using for instance aegis of menhir for fire+physical damage all the way to 94, then use a legendary set to convert it all to physical but then you need to add in another random skill in the mix to keep doing some form of elemental damage. Seems like bad design or something doesn't add up.