also because walrien has significantly higher hp than defenses he is one of those unique pokemon where maximum balanced bulk does not come from fully investing in hp. kind of like how its a bad idea to max out hp and atack on cb snorlax because it could get more overall defense by divying up its evs among its defenses and hp (idk the exact spread).
The HP to defense gap is actually not big enough for this to actually be true - Max HP does actually help maximize overall bulk.
This is the spread I use 252 HP / 96 Def / 52 SpD / 108 Spe; Bold Nature
. This maximizes bulk with a slight emphasis on physical defense (55% Physical
). It has enough Speed to beat min Spe Blastoise, which is enough, imho. Trying for Suicune's speed tier is just a bit excessive.
I can vouch for Toxic's effectiveness; it makes Walrein a lot more self-efficient and less hazard-dependent. Understandably Roar is the superior choice, since it can wear down the likes of Rest Talk Lax, CroCune, and Umbreon much more readily if the hazards are down.
Super Fang is AC material, though.