That's right. But some skills complement each other and others oppose each other. I doubt anyone here has bought more than one melee, one ranged and one shield Expertise. There's no point! You can only use one melee weapon at a time, so why specialise in five different types? Also, a Warrior doesn't really need to take the Deadly Gift skill. He has enough health and strength to defeat enemies without assistance.
On the other hand, a combination like Bow Expertise, True Shot, Ranger's Sight and Explosive Arrows is a very beneficial combination! When skills are presented, there is often a plan behind them. It's not mandatory, but it is of great assistance.
How far trough the game would you get if you bought one point in every skill so you could have a chance at any situtation? Not very far, not very easily. You need to specialise in something to get you through the majority of the game and have a backup plan to fall back on.
