[RPG] 5e Shapeshifting Druid rules

Here's the text of the Gnoll's ability (as found on page 317 of the pdf SRD):

Rampage. When the gnoll reduces a creature to 0 hit points with a melee attack on its turn, the gnoll can take a bonus action to move up to half its speed and make a bite attack.

And Wild Shape says:

You automatically revert if you fall unconscious, drop to 0 hit points, or die.

In order for the druid to revert out of wild shape, they have to drop to 0 hit points. If they do so as a result of the gnoll's attack, it clearly did drop a creature to 0 hit points, and should be able to use Rampage. The fact that the creature suddenly turns into a different one that has more than 0 hit points doesn't matter.

A Medium humanoid druid that employs the supernatural ability wild shape to assume a Medium alternate form can, for example, consume a potion of enlarge person to gain that spell's benefits—like becoming Large and a +2 size bonus to Strength—while in that alternate form.

If that same (normally Medium but currently Large) humanoid (but having assumed an alternate form) druid then opts to end the wild shape effect while the enlarge person effect's duration continues, the druid resumes his normal original form except that the druid's Large as per the spell enlarge person until the enlarge person effect ends. (N.b. the spell enlarge person is dismissible.)

Were that same druid to then employ wild shape again to assume a Medium form again, he would assume that Medium form, the special ability wild shape setting his new size category overruling the ongoing enlarge person spell effect (q.v. One Effect Makes Another Irrelevant and—more tellingly—the omitted-from-the-SRD examples on PH 172).

So you know, this DM would likely rule that were the Medium humanoid druid to employ initially the supernatural ability wild shape to assume a Large or bigger alternate form, consuming the potion of enlarge person would have no effect. The enlarge person spell's description says, "Multiple magical effects that increase size do not stack" (PH 226), and the supernatural ability wild shape is, indeed, magical, therefore having the same constraints on its interaction with the spell enlarge person as any other magical effect.

However, this player wouldn't argue with a DM that ruled that because the supernatural ability wild shape sets a druid's alternate form to particular size that an enlarge person effect could work normally on that druid. That is, the supernatural ability wild shape doesn't change the druid's size but puts the druid's size at certain point and the enlarge person effect works from that point. This player may point out that this gives the druid an edge when employing size-changing magic—which is already pretty awesome—, but, since druids are involved, I don't think this ruling would even crack the top 10 list of Things I Worry About When Fighting Druids.