Having driven into Boston from the Wellesley/Needham area for years, the time of day that you are driving will be important (as indicated in the earlier answer too).
As for cutting across Route 30 - you always have tons of company if you are driving at peak times (everyone from Weston/Wayland headed for the Pike will be sharing the road. On most days, you will sit for several cycles at the light at South Ave (Rt. 30) and Newton St. and again at Rt. 30 and River Road, where you turn to get onto the Pike. As you note, taking Rt. 30 will avoid Rt.. 128, but it will not save time necessarily. The 128 stint may be less frustrating on most days.
If the commuter rail were an option (which I understand it may not be depending on where in the city you work and your need to have flexibility in terms of time etc.) being near Needham and Wellesley at least opens up the options of two train lines (although the schedules are not that different). If it ever becomes an option, the Needham commuter rail line is a little faster than the Wellesley line in general.
I wish I had a great alternate route/plan to offer, but unfortunately, no matter where west you live, you have a good amount of companionship commuting into Boston. If I can offer any additional information, please just let me know.
Showpiece Real Estate, Inc.
Serving clients in the communities of Wellesley, Weston, Needham, Newton, Sherborn, Natick and beyond.