You can just check in stats or d2stats if keeping colonel as offhand adds 500% ewd to your EWD stat.
If this only works as main hand, I'm not convinced if in this case it would beat very high damage main weapon. Yes you lose 500ewd, but you are basing your whole damage off fairly low base flat phys. Your total ewd is still high, you get bunch from wolf stance/spirit guide, over 500 there, and then from strength (160% per 1000str, so 800 with 5k str for example). Colonel only adds 500 to that pool so thats not that much, if your total ewd is 1500, adding 500 from colonel is only 1/3 of your total ewd. And you can replace it with weapon thats gonna have double colonel's base damage.
200ed +300 max damage 2h sword, this will be what, 190-500 damage as one hander. Snowstorm makes it 240-600 (420 avg) and thats what you should compare to alternative 2h. In comparison colonel base damage avg is only 144 (220 with snowstorm shield). For instance Gotterdammerung with 6 jahs would be 570-760 damage (665 avg), so still better average than that by over 50% (and 3x more than colonel with shield) and that with mega impact and aoe which are pretty significant.