It seems both Grishnak and the DM are to blame in this problem but I do think the lion's share of the problem belongs to Grishnak.
A Ranger 7/ Shadowdancer 9 is about as bad a frontline fighter as you can design. You shouldnt expect to make a huge combat impact when you are playing a party scout.
Your build is giving up 5-7 points of BAB over a straight up fighter. Its unfortunately true in 3E but despite spending 3-4 feats TWF is still a vastly inferior fighting style for what you get, especially now that WOTC seems determined to make it a combat style only valid to rogues. Especially when facing off against high AC opponents that -2 points to BAB is brutal. Try to talk your DM into allowing Improved ambidexterity or its equivalent into your campagin world which reduces all TWF penalites by 2 (to -0,-0 or -2,-2 respectively). That would at least make the combat style worth all the feats you have to flush into it.
Also, your character seems tied to a vastly inferior magical item, and although it is not helping it's fine from a character stand point. If the weapon is THAT important to the character then consider having one of the party Wiz/Clr buffing it during downtime. Add Flaming + Frosting or some other combination of elements is always nice.
If you are still set on the Ranger/Shadowdancer idea then ask your DM to allow you to redesign the character a bit. Go with Ranger 12/Shadowdancer 4 and place more focus on STR and less on DEX. You lose only a single point of BAB, are just as good at sneaking, and get the flavor of the Shadowdancer without the useless called shadow.
Good luck...