My invested CON was 100 which gave me around 45k HP in total inside TBL arena with a Nyx set (I was too lazy to farm sh*t), Lionhead Shield, and Swashbuckling on. I think it was 60k+ outside of TBL. It was enough to survive most OHKO skills. The only one that killed me in one hit was a very, very well-geared HopMurm.
I got 100 in DEX too for block pen since again I was too lazy to make/buy high-level yellow gems for gloves (only used lv.5). I was wearing 2 x glass bracelets to compensate. I thought block pen was really necessary in the build (for PVP) because it doesn’t have skills or attributes that improves that substat AFAIK. Evasion from DEX is useless in the build because Finestra negates it. Skill animation speed improved a bit as well (compared to not having DEX at all) which helps with skills having overheats.
The rest went into STR (100+) because, again, of my lack of damage from equips (Trans lv.4 +11 Pevordimas Spear, some +pAtk headgear) so that helps. I can pretty much one-shot players with the same or slightly higher gearing level than me (Synchro, Scutum, Headbutt, and Frenzied Slash sometimes which is very cool to witness, reminds me of the Achilles vs Boagrius scene in Troy). Another important reason was for accuracy against most Archer builds.
I think the Sword tree and some archer builds really got the short end of the stick with the stat rebalance. On equal gearing, a lot of Wiz and Cleric builds can get away with very high or full CON while still dealing decent enough damage.
You can probably still go the full CON route though, but that’s gonna require a really high investment in gear.
(EDIT: This information was until June 2017 so things might have changed)