Views RSS post date removal
This approach should work. I've tried it in the past and it did exactly what I needed.

Quoted from the above-linked comment: 

Put views-view-row-rss.tpl.php in your theme directory

and replace print $item_elements; 

with

$item_elements = preg_replace('&lt;pubDate&gt;.*&lt;/pubDate&gt;', '', $item_elements);  // removes pubdate
$item_elements = preg_replace('&lt;dc:creator&gt;.*&lt;/dc:creator&gt;', '', $item_elements);  // removes author
$item_elements = preg_replace('&lt;category .*&lt;/category&gt;', '', $item_elements);  // removes terms         

$item_elements = preg_replace("!^\s+(\D)!m", "\\1", $item_elements);  // removes some blank lines

print $item_elements;