I think they did a little more than allude to it.
Only way they could make it more obvious is have Gwen torch Gelph with psychic power.
I think they more dropped the ball by making her fairly pointless. At best, she's the heart of the group, but we're given no reason for her to be. I think if
"Spoilers, sweetie,"
Gwen had died instead of Ianto, there would be dancing in the motherfucking streets. Actually, pretty much every other member of Torchwood 3 had been given roles as actual sympathetic characters I could believe the team would rally around.
Gwen? She's kind of like a stand-in.
Plus,
what kind of lame power is heart, anyway?