Virizion does none of these things. It's a sweeper. Virizion is the only Grass-type in the tier that can use Swords Dance, and it does it pretty well. It can use either Hidden Power Ice to break through Gligar, or it can nail Zapdos and Crobat as they switch in with Stone Edge. While its typing is terrible on the defensive end, it has pretty good Offensive STAB, Flying is the only type that resists both, and Stone Edge covers it very well. Calm mind is also decent, as Virizion will have a somewhat decent form of recovery, thanks to Giga Drain. It does have to unfortunately use Focus Miss for fighting STAB, but if it hits, it's going to hurt. A lot. Virizion is also the only grass-type that can set up Dual Screens, and it can use Taunt, which could give an offensive team momentum right off the bat. Or it could use Work Up (lol).
Sceptile is an arguably better grass SD sweeper due to Acrobatics and Unburden, as well as its' natural 120 base speed. Virizion is not the only grass type that can use Dual Screens, and Meganium is arguably better due to its' access to Aromatherapy and Leech Seed (I don't think Virizion gets LS?). Also, Virizion's dual STAB is also resisted by mono-bug types, which gives an easy switch in to the resident king of UU... The Beast, the LEGEND, HERACROSS!!!