>>43331623>Also how does investing in def/spdef compare to HP investment in terms of bulk?Look up the pokestudio calculator, Hiro won't let me link it but it's quite useful.
The general rule for tanky Pokemon should be to max out (or max to 248, more on that) HP first and then defenses. The main exceptions are Pokemon with very very high HP relative to their defenses (think Chansey, which also gets Eviolite of course) and non-defensive Pokemon that are just trying to live one specific attack in the fewest EVs possible (it takes 80 HP EVs to take Keldeo out of Draco range from Specs Dragapult, for example, but only 52 SpD EVs).
>I've heard that there are more optimal number values than others but I don't get it.It's all about percent damage like the other anon said. The easiest rule to follow is just to avoid even HP values; residual damage all comes in multiples of 2, so if your health is equal to a multiple of 2 + 1, you're getting a free extra hit. Volcarona with max HP gets 2-shot by Stealth Rock, for example, so bulky Volcarona should always go 248 HP instead of 252. Most mons can safely go 248 and gain a theoretical edge for it, since 1 HP ultimately isn't a big difference. The only complication is Leftovers on mons whose max health is divisible by 16, since going for max health - 1 means you lose 1 point of Leftovers recovery each turn. Going 252 is generally fine then.
