Atarlost |
The trick is that centaurs, being large, run afoul of the polymorph rules and the weakness of polymorph spells compared to the standard size modifiers.
You need to subtract 4 str and 2 con and add 2 dex before applying the modifiers of any polymorph spell. That means you actually lose HP going into any form without a con bonus (ie. anything but a plant or some elementals) and will be terrible at strength.
This means you basically have two choices: Abandon wildshape and go strength based (consider natural jouster) or do scimitar dervish dance (usually air elementals are best, but fire elementals won't reduce your con)
In either case Powerful Shape is not worth it.