When using savage colosseum, certain card destruction life gain effects are negated.

When using savage colosseum, certain card destruction life gain effects are negated.

Both cards use the word "When" which means that they can miss the timing. This is exactly what happens if you combine them with something like Savage Colosseum. It goes like this:
1) The card gets destroyed
2) Savage Colosseum activates
3) You can't activate the card because the last thing that happened was 2) instead of 1).

Not sure if you should remove Colosseum or the monsters. The deck is very gimmicky anyway and it's your decision if you want to go for full burn (remove Colosseum) or want to play more mind games (keep Colosseum). I guess the full burn strategy is better.