Quote Originally Posted by Tavrobel
However, you can't actually get all 256 rages because there are 3 monsters who have rages, but are never activated on the Veldt.
...and a monster (pugs) who has a rage and is activated on the veldt,but does not appear in your rage selection screen.so all in all,there are only 252 accessible uncheated rages.

and to answer your question,yes,monsters will appear on the veldt even if you run away from them.