Well , it depends the level of difficulty one plays IMHO
One thing to keep in mind is that you have only 28 points that you can spend "freely " , the rest is necessarily in training (34 total points - 6 )
the other thing to keep in mind is that the most powerful talents are at the end of each tree except 3 of them ( boosted mutagens , boosted potions , and additional vigors )
Another factor is that the most powerful stuffs are "attribute boosting" talents , so mutagens , potions , damage/vitality/vigor and adrenalin boost ,
Finally , the most useful talents are achieved only when you put the second point , if you put only one point in every skill , you are going to be weaker than someone who has less talents , but has spent 2/2 on the most powerful talents
Personally , my experience is that spreading into 2 trees produce the most powerful build ( namely Alchemy-sword build , with for instance 18 in alchemy and 10 in sword you end up with 10 mutagens with doubled stats (mutagens really shine when you double their power and have more than 5 slots , 10 slots is ideal ) , fastest adrenalin charger , highest HP or armor or criticals depending which mutagens you applied , can drink 4 super potions , stack the damage/vigor regen/adrenalin bonuses of sword tree and alchemy tree etc .. )
Magic-sword , or Magic alchemy is powerful too , especially magic-sword . But spreading into 3 trees in my opinion and experience is the weakest thing you can do (even though you can still finish the game easily as it is almost impossible to "screw" a build in TW2) , because even though you can have a few interesting talents from each 3 trees , you won't get the "absolute best " of 2 trees , so it can only be weak due to the fact that there are only 28 points , well IMHO .
Going full specialization in only one tree is powerful ( and easy to play at the beggining if you go full sword ) , but not the most powerful in the end because you stack nothing from two trees .
Generally speaking , a strong pure mage will be almost invincible in 1vs1 (bosses ) , but more "vulnerable" against powerful mobs (because of limited vigor ) , whereas pure sword build will be "generally speaking " less strong against bosses but will breeze through the mist and encounters where you are facing groups of enemies (thanks to whirl , +dmg with sword etc ) , so going for a hybrid build with points invested in two trees gives you the most "flexible" build too , well just my opinion
Post edited June 22, 2011 by Ianis