The tax issue obviously depends on where you live. Some places there is no tax on cryptocurrencies (lucky bastards!). Other places thay have to pay tax on every transaction. Even when buying cryptocurrencies with other cryptocurrencies. This is hopeless. But using the TenX card doesn`t make it worse. It might make it easier, even. Because after trading hundred of times between cryptocurrencies on exchanges, by the next tax return, I have to trace every single trade and calculate loss/winnings. I am not looking forward to this. However, if I instead would just buy ETH with fiat, send it directly to my TenX wallet, yes, I would have to pay taxes on every transaction when using the card, but then I would easily know how much. I would just have to add all expenses by the next tax return and whatever amount exceeds my original purchase amount, I would have to pay taxes on (I am assuming they will have a way of seeing your total monthly or yearly expenses here, like normal credit cards do). I hope this makes sense.
Also, you should read this. The real benefit of the TenX card: