i use warm & natural and don't seem to be having a problem - I'm quilting Grandma's Flower Garden and i'm always quilting thru seams because of the hexagons!
The quilting group I go to also uses the warm & natural. I don't like the poly batting that joann's sells - it's too loose - odd description, but i don't like it because the needle falls thru and i can't get my rocking motion going for small stitches.
Try a new needle - I was beginning to have a hard time and changed the needle and it went thru like butter