Embarked VT-8 aircraft launched against Nagumo's Kido Butai was 15 TBDs. Land based VT-8 detachment included 6 TBF-1s. The 15 VT-8 and the 14 TBDs of VT-6 also came in unescorted. Actually VT-8 ( VT-6?) had an escort of 10 VF-6 F4F-4 but unlike the Yorktown's air group, the Enterprise and Hornet launched individual squadrons that proceeded to the target area and executed uncoordinated attacks. VF-6 CO Jim Gray didn't coordinate his arrival with that of the slower aircraft of VT-6. He orbited at 20,000 ft awaiting a call for assistance (which never came) until he was low on gas and returned to the Enterprise. Needless to say he caught some heat over this. I agree the SBD was effective and a hard target for sure, and for a variety of reasons.
But mainly I believe their success was due to the IJN's inability to mount and coordinate an effective high altitude CAP due to their lack of a RADAR fighter direction system (thank you very much Commonwealth cousins), which was a problem throughout the war. The SBDs virtually always got through, in part because they were an excellent platform but also because they faced an opposition that was determined but diffuse in its execution. Of course, on occasion there were some losses, especially on egress from the battle area. By comparison, in the afternoon, flying against the Hiryu, some 24 SBDs successfully attacked a carrier defended by more than a dozen A6Ms, suffering relatively light losses. This can be compared to the 18 VALs that attacked the Yorktown which was defended by approximately the same number of F4F. Only about 5 VALs survived the attack. While the VAL lacked armor SST, it was reported to be exceptionally maneuverable.