Was it the 40mm long strips? I haven't heard any complaints from my caster with the 2-man strips.
It's the scale. Ideally the weapons need to be 10mm scale, with thin shields and tiny holes between arms and weapons etc.
When Colin got a job in the studio he said to us "don't worry, i know mouldmaking, you won't get difficult masters from me!!" ....... his first project was warmaster lol
Also with the amount of castings that GW produces it puts a strain on the masters, and they need to be recast, which puts a strain on the master moulds. I know a lot of the master moulds were on their last legs, so it wouldn't be as easy as "let's just keep the range we have, and expand on that with races we haven't done before". You'd have to redo everything.
At the time we were using black rubber, which i personally think is worse then the silicone moulds that most companies use nowadays.
This whole project is run by Tony Cottrell (dunno if he's known?) .... Head of Forge World ... basically he is very much into 40k, not that bothered about fantasy setting (WHFB, WM etc)