Can't hurt to try. Well, actually it CAN, like if you get fireballed without your 25% resist shield, but bear with me. As a Ranger you already have ** in two-weapon style as a class ability, meaning that adding a second weapon won't change your primary attack's THACO at all and you will be only -4 to hit for your off-hand attack. (Investing one more * to go up to *** in two-weapon would reduce that penalty to -2 if you chose to.)
As for whether it's wise to stick with it, I'd say it depends on the rest of your party, your preferred tactics, and whether you've got a really good secondary weapon to use (or are planning on getting one). There's also always the option of switching back to a shield for specific battles when you know you'll need the AC, resistances, or immunities from the shield more than the extra attack. More damage is always fun, but as Six pointed out, maximizing one character's damage isn't necessarily wise if it comes at the expense of making your party overall more vulnerable.
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->Klutz
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