Isengard will remain much the same unlike the other original factions they don't lose any units or heroes instead they gain quite a few new ones.
Isengard gains a few new units such as the Heavy Shield Uruks,Uruk Bowmen,Isengard Orc Rabble,Uruk Captain and the Dunland Wildmen.
One of the most noticable changes to Isengard is the amount of Heroes gaining 5 new heroes like Ugluk,Mauhur,Sharku,Grima Wormtongue and Wulf.
The new heroes aren't overly strong so Isengard will still not be hero based faction.
Saruman has been powered up significantly with 4 new abilities 2 Magic attacks,Leadership and a Crebain Summon
Grima Wormtongue is a great support Hero especially to Saruman. Grima becomes stronger when nearby Saruman (Grima's Shank ability is a 1 hit kill against Saruman even an ally Saruman)