poolbound gems cause special effects of gems(chain hit, poison, mana leech) to be boosted insanely.ex. lvl 18 red-orange. 12.54 chain, 1.3k mana leech. lvl 18 red-orange-white 154 chain, 10k leech (both examples are while in traps with 20 on trap skill)
Added: poolbound in amplifiers not a good idea.
Too much power:
Added to a low level gem:
To kill these types of enemies:
Had to pause at that moment to prevent flash from crashing. too many shots per second.
Poolbound is great at first. I use it to craft my initial, throwaway killgem and managem.
Unfortunately, Poolbound's effect increases slowly. The other gem-enhancing gem, Bloodbound, starts off much weaker (and its Hit Level will never rise to match or exceed the Mana Pool level during normal, sensible play) but its growth is much faster. So much so that around Grade 30 or so you will want to completely rebuild your gem with Bloodbound instead of Poolbound!
You are correct in not wanting to put Poolbound (or Bloodbound, for that matter) into an Amplifier. The ___bound effects are not boosted by the Amp. That is not really a bad thing though.
Your trap gem shows that your 5 amps are giving it +456,297.4 manaleech. Each amp, therefore, is providing 20% of that - which comes out to 91,259.48 each. That is a lot less than the 21% of 2,661,079,597.79 (which is 558,826,715.536). The explanation for the difference is that the base amount, not the displayed, after-bound amount, is used. 2,661,079,597.79 / 6965.34 = 382,045.90 .... 21% of which is 80,229.639. That is in the ballpark, at least (though it shows that there's a little more to the mathemagics involved than these simple calculations).
So, instead of attempting to boost the manaleech through a bound special, boost it through supergemming instead. Make a much more powerful pure gem to provide even more mana leech to your trap. Now, my skills are apparently higher than yours (based on your pics) but just through the 64 gem upgrade I was able to create a displayed grade 31 orange gem with 1,755,289.37 mana leech, that cost 3,710,851,743,696 mana. More than four times the base mana leech at less than a twelfth the mana cost.
I'd recommend you check out psorek's high end guide for gemcraft chasing shadows. You will find a lot of good information there, and from your pics, you're at the point where it will help.