I could be wrong here but the impression I had was the Ishamael knew from the begining that if is body perished he was pretty guaranteed to be recycled by the Dark One. It seems clear as the series goes on that of all the forsaken only Ishamael is on the same wavelenght as the DO when it comes to the end game. The rest of the forsaken are out for themselves but Ishamael wants to see the world destroyed same as the DO which makes him pretty valuable to the DO above and beyond the regular forsaken.

If he was guaranteed a new body if things went south then all he has to watch out for is balefire and aside from that if he dies... so what he knows he gets a new body.

As far as the rest of the forsaken, they made their reputations as leaders of the Shadow in an Age when they have probably millions of people backing them. They struck me a lot more like some of the mort important Nazi's some were generals others were twisted doctors, PG guru's etc. That does not make them individually great fighters. Himler was pretty feared but if you plant him down in a world where he does not have several hundred thousand SS and give him a big gun he may not match up so well to an elite solidier.