It would only be a problem if they gauges suddenly needed to draw more current (like a car stereo amp that hits a huge bass note), which should never be the case.
Also might come into play if you battery gets to low (but by that time your car would be dead), you might notice your gauges staring to malfunction.
So really there isn't anything to worry about.
I personally don't like the grounding wires all tapped together, but again, not something to really worry about since the gauges and their lights don't draw that much current.
