I know I might be alone with this, but I think the best thing that ever happened to Marsanne is Roussanne. Roussanne brings acidity and herby spice to the party and counterbalances heavier more viscous (less acidic) Marsanne. It sadly is losing place to Marsanne due to being more temperamental and thus more difficult to grow.
However, single varietal Rossanne is a delight be it from the Rhone (like the much covetex Beaucastel Vieilles Vignes), Australia or South Africa. The latter I recently tried from TWS:
Left me wanting more…
Had much less luck with single varietal Marsanne, would not call the ones tried lively, except for:
Which is actually quite refreshing.
Rhone grape varietals rule!