Plently of pokemon that require support, such as Rain support for Kingdra and Kabutops, are placed in higher tiers. Ampharos needs wish support, but it ends there. It's bulky enough and powerful enough to both be a pivot and eliminate common and powerful threats. Similar in function to CB and AV Scizor. While life orb scizor/leftovers scizor/mega scizor has roost, his two most common sets do not. I think that should be a good enough argument for powerful pivot switches that also happen to be slow. AV Scizor, specifically, is probably the best example of this. They need some support, yes. But they can still be very dangerous.