I thought it was commonly agreed that she needs more appearances. Nobody else thinks so? :(

I can agree with the 2nd part,  
But, she’s the only character to have had a speaking role in every single episode of Season 3 and in Season 4 has played prominant roles in “Princess Twilight Sparkle”, “Castle Mane-ia”, “Bats!”, “Pinkie Apple Pie”, “Simple Ways”, “Somepony to Watch Over Me”, and now “Leap of Faith”. And the only episode she hasn’t been in is “Flight to the Finish”.
 
Really, it’s not quite the “Twilight Sparkle Show”. Recently, it’s been more “The Applejack Show”.

@PonyPon  
Not nearly enough.

Where’ve you been, she has plenty of screentime.

Yes yes best pony Derpy agrees.