Raising dexterity and finding way for sufficient AP to have meaningful actions is all. As game progress rangers will naturally raise steadily. If it cost nothing to benefit party, developing instead of rushing and getting no meaningful actions. Ranger have huge array of possibility on how to go about things not excluding supplementing with spells or consumables, waiting for perfect storm. Its possible to find crossbows' 1-4 higher lvl of yours and boost it with lvl 3 crafting and it will be long before needed Bow ability points come but in that time one could be happy to use +1 crossbows' item if found and have fun with AoE bursting damage. Some skills got fix AP cost and same go for special arrows.
Now while its true that Bows are superior as Marksman skills and special arrows can never crit (it usually implied that it also ignore hit chance), there are thresholds on what you invest and what you get especially early game. Idk for all the skills but this part is huge when compering with Man-at-Arms for example, Splintered Arrow and Ricochet scale not only from weapon but also from Dexterity. Crossbows' cost 1 AP more to use then bow, slow your move speed and have higher base weapon range and damage and scale crit chance and multiplier, bow scale % damage.
