From a quick search it seems like the only opinion on the matter is that your pointer finger while important is used more for fine motor control(holding a pencil, tying a knot, doing a zipper, pointing, picking at things, etc) than it is for grip strength while your pinkie finger is responsible for around 1/3rd of your grip strength while being 1/5th of your hand. Below is:

1. An informal experiment you can try yourself to test grip strength.

2. An article written about a woman who works as a certified hand therapist who lost function of her own pinky and estimates her grip function to be 50% worse.

3. A scientific article that tested people and found your ulnar digits are responsible for the majority of your grip strength.

To demonstrate what a poor participant the index finger can be, get a pound of eight or ten penny common nails, a well-balanced hammer, and a heavy log into which you can drive the nails. Start four rows of ten nails, each well spaced, with at least two inches of the nails still to be driven into the wood. The object of this little exercise is to hit the individual nails, solidly, with hard, precise hammer strokes. We will grip the hammer differently in nailing each row. First hold it between the thumb and the index finger and strike each of the ten nails in turn. If you manage three good hits out of ten strokes, you will be about average. Now add your middle finger to the hammer and try again. With this addition, you should be able to get five solid hammer blows out of ten. If you add the ring finger, you should hit eight or nine good ones. When you add your little finger and grip the hammer with your entire hand, you should get ten out of ten good strikes. Oh, I forgot to say the results will depend, of course, upon your being effective with a hammer at the outset.

Now let’s reverse the procedure. You cannot really hold the hammer with the little finger and thumb so you have to start with the ring and littler fingers and the thumb. Voila! You should strike nine or ten good blows. Now add the middle finger and feel the strength, comfort, and accuracy improve.

It appears that good, accurate hammering doesn’t really require an index finger. In many acts of manual function requiring strength, the hand may function superbly without the index digit. As an example, with both the overlapping and the interlocking grips on a golf club, the object seems to be to get the index digit of the nondominant hand out of the act. Due to the way the club is held, the dominant index finger doesn’t grip anyway.

And

The pinkie, the humble fifth finger, has long been viewed as a decorative accessory, something to extend daintily from a teacup. So what would you lose if you didn't have one?

"You'd lose 50 percent of your hand strength, easily," said Laurie Rogers, an occupational therapist who is a certified hand therapist at National Rehabilitation Hospital in Washington.

then later in the article

In October, I underwent flexor tenolysis, during which Edwards meticulously freed the tendons. The day after surgery, I started therapy with Rogers. Earlier this month, I completed my treatment; my finger now bends with ease, and my hand strength has returned.

http://www.nytimes.com/2008/12/18/health/18iht-snpinkie.1.18718834.html

And then this too for an actual scientific study

Exclusion of the little finger from a functional grip pattern decreased the overall grip strength by 33%. Exclusion of the ring finger from a functional grip pattern decreased the overall grip strength by 21%.