I would say, in my opinion, no.
For starters, all it does is decrease one damage, which really doesn't help all that much in a life deck (pffft, 23 damage? I heal that in my sleep.) Secondly, it prevents creatures with one attack from dying. Perhaps this is a minor gripe, but I just hate when a parasite is dropped. Thirdly, it doesn't decrease cost, which means you won't get it out any faster anyway.
Thorn Shield's real use is creature killing. Adrenaline their otyugh and then watch it seppuku into your spiky safety. If you don't want creature killing, emerald shield is better. If you do want creature killing, thorn shield's upgrade kills less creatures.
The two best shields to use are Jade shield and Thorn shield. An upgraded spike shield would only make your deck worse.
Still... my best advice is to try the trainer first, and see what you'd prefer.
