I've had times where I kept losing a paticularly tough fight, like the Splitpaw Solo Arena Champion, and potions made all the difference. Damage Shield potions were more useful than HP or Power regen - they tend to be miserly with the amount they restore. Like every individual buff/debuff/gear upgrade in EQ2, they give a small, incremental boost. You get nothing spectacular from any one, in fact it may not even be noticeable, but when combined you will definitely notice. (Not counting diety miracles.)
Totems feel more useful to me, they give a 30 minute buff to pools and OOC regen, and the run speed totems are as good as the starter horses and WAY cheaper. J-Boots and a totem give 34% run speed increase for next to nothing.