Hmm. Since SR has no inset enhancable Resists, and Brute and Scrapper (and Stalker) have 3/4 base values thats a whole lot of set bonuses. Tankers get a lot more out of Tough, and the ATO adds resist
But its mainly overkill, having played Scrapper, Brute and Tanker SRs to 50, they all can pretty much handle most everything thrown at them with IOs once they actually get their AOE toggles. Sadly for Scrappers that's pretty late.
SR tankers do have one distinction, in that they can easily softcap at a very low level without many IOs, and thus exemplar better than a lot of tanker sets.