Lol its not always easy, in this particular game we got all creeps but 1 warg, so wasn't hard to get white. But If mor isen wants to they can usually creep both wargs before horses are out, and they can maybe even steal a troll or 2, if mordor goes haradrim, which is not what you normally see, mordor will take all creeps. Imo if mor isen creeps well 2 gondors are in trouble . Also pit start is rly effective here for isen, since if gondors double land, they wont get white in a very long time unless isen starts feeeding pikes.
This blue isen was pretty weak but you did good. You could have easily killed Lurtz when your gandalf was out as Lurtz was lvl 1 and on your side with only 1 pike with no ups. Also I think it would have ended way faster if none of you had cashfloated and made archer after gtw as they basically had only some pikes, some trolls and lurtz until late game.