Inexpensive and accessible, Hired muscle seems like a bad card due to it's drip expense.
The funny thing is that hired muscle IS a bad card.
Other cards exist that grant +1 to their respective ability and no other benefit except tanking capacity, the best comparison would be the Holy Rosary.
So, a comparison of the two:
Hired muscle has 2 extra total hitpoints.
Holy rosary occupies a less competitive slot.
Holy rosary does not cost XP.
Hired muscle costs 1 less to play.
Holy rosary does not drain 1 resource every round.
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So, the ultimate difference is that hired muscle has 1 disadvantage, the cost drip, and this disadvantage eliminates the cost advantage immediately at the end of a round and then keeps scaling negatively. The cool thing about slotted upgrades is that they stick around to give you their benefit for a long time, and are at the ready to provide the benefit even though it wont be needed for a few rounds. Hired muscle doesn't have this benefit, you by no means want it around round after round.
Hired muscle is the one slotted ability bonus that keeps costing you after you play it, Thus acting more like a resource pumping Talent like Hard Knocks then a lasting item bonus, and frankly speaking Hard knocks is much more likely to net you successes in the long run than Hired muscle. This means that Hired muscle´s only remaining ability is to soak damage, and even then the rampaging cost hardly justifies that either.
To mitigate Hired muscles cost you really want to get use out of it quickly. Play the card, knock some heads, then get it killed, but to get it killed you need to stick around and get hit by an enemy, an enemy that cards like Hired muscle would ideally help you get rid off (also, if you're TRYING to get the card killed then the health isn't much of a benefit.
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At this point you've probably got the idea. Hired muscle is weak and counter-intuitive, ALSO you have to pay precious XP to slot it.
Don't ever bother with this card.
Ever.