Half Bloods are almost redundant.
They give less electrum (in terms of time) than AI3s
They give less rares than T50
The chances of winning a card (not even mentioning upgraded cards) is low compared to all others.
The only use is to practise long game strategy (for people with newly made FG decks). But that's what the trainer is for, and the trainer will prevent any loss of electrum.
My Suggestion: Half Bloods should have 150 health, and 20-25% upgraded cards, to make games faster, make them stronger, and increase chances to win upgraded cards.
Discuss.